diff --git a/CHANGELOG_PENDING.md b/CHANGELOG_PENDING.md
index b85173436..3ccf61fb1 100644
--- a/CHANGELOG_PENDING.md
+++ b/CHANGELOG_PENDING.md
@@ -29,6 +29,8 @@ Friendly reminder, we have a [bug bounty program](https://hackerone.com/tendermi
 - Blockchain Protocol
 
   - [types] [\#4792](https://github.com/tendermint/tendermint/pull/4792) Sort validators by voting power to enable faster commit verification (@melekes)
+  - [evidence] [\#4780](https://github.com/tendermint/tendermint/pull/4780) Cap evidence to an absolute number (@cmwaters)
+    Add `max_num` to consensus evidence parameters (default: 50 items).
 
 ### FEATURES:
 
diff --git a/abci/types/types.pb.go b/abci/types/types.pb.go
index 1d23a04a9..2572d8d8f 100644
--- a/abci/types/types.pb.go
+++ b/abci/types/types.pb.go
@@ -2644,6 +2644,7 @@ type EvidenceParams struct {
 	// Note: must be greater than 0
 	MaxAgeNumBlocks      int64         `protobuf:"varint,1,opt,name=max_age_num_blocks,json=maxAgeNumBlocks,proto3" json:"max_age_num_blocks,omitempty"`
 	MaxAgeDuration       time.Duration `protobuf:"bytes,2,opt,name=max_age_duration,json=maxAgeDuration,proto3,stdduration" json:"max_age_duration"`
+	MaxNumEvidence       uint32        `protobuf:"varint,1,opt,name=max_num_evidence,json=maxNumEvidence,proto3" json:"max_num_evidence,omitempty"`
 	XXX_NoUnkeyedLiteral struct{}      `json:"-"`
 	XXX_unrecognized     []byte        `json:"-"`
 	XXX_sizecache        int32         `json:"-"`
diff --git a/abci/types/types.proto b/abci/types/types.proto
index f935645ac..50c77cde0 100644
--- a/abci/types/types.proto
+++ b/abci/types/types.proto
@@ -302,6 +302,7 @@ message EvidenceParams {
   int64                    max_age_num_blocks = 1;
   google.protobuf.Duration max_age_duration   = 2
     [(gogoproto.nullable) = false, (gogoproto.stdduration) = true];
+  uint32                   max_num            = 3;
 }
 
 // ValidatorParams contains limits on validators.
diff --git a/consensus/reactor_test.go b/consensus/reactor_test.go
index 3c3eef7ed..d5f336868 100644
--- a/consensus/reactor_test.go
+++ b/consensus/reactor_test.go
@@ -209,7 +209,7 @@ func newMockEvidencePool(val []byte) *mockEvidencePool {
 }
 
 // NOTE: maxBytes is ignored
-func (m *mockEvidencePool) PendingEvidence(maxBytes int64) []types.Evidence {
+func (m *mockEvidencePool) PendingEvidence(maxBytes uint32) []types.Evidence {
 	if m.height > 0 {
 		return m.ev
 	}
diff --git a/consensus/replay_stubs.go b/consensus/replay_stubs.go
index 762a0948e..542b9d6f1 100644
--- a/consensus/replay_stubs.go
+++ b/consensus/replay_stubs.go
@@ -50,11 +50,11 @@ type emptyEvidencePool struct{}
 
 var _ sm.EvidencePool = emptyEvidencePool{}
 
-func (emptyEvidencePool) PendingEvidence(int64) []types.Evidence { return nil }
-func (emptyEvidencePool) AddEvidence(types.Evidence) error       { return nil }
-func (emptyEvidencePool) Update(*types.Block, sm.State)          {}
-func (emptyEvidencePool) IsCommitted(types.Evidence) bool        { return false }
-func (emptyEvidencePool) IsPending(types.Evidence) bool          { return false }
+func (emptyEvidencePool) PendingEvidence(uint32) []types.Evidence { return nil }
+func (emptyEvidencePool) AddEvidence(types.Evidence) error        { return nil }
+func (emptyEvidencePool) Update(*types.Block, sm.State)           {}
+func (emptyEvidencePool) IsCommitted(types.Evidence) bool         { return false }
+func (emptyEvidencePool) IsPending(types.Evidence) bool           { return false }
 
 //-----------------------------------------------------------------------------
 // mockProxyApp uses ABCIResponses to give the right results.
diff --git a/evidence/pool.go b/evidence/pool.go
index c3708447f..f086f66b2 100644
--- a/evidence/pool.go
+++ b/evidence/pool.go
@@ -82,8 +82,16 @@ func NewPool(stateDB, evidenceDB dbm.DB, blockStore *store.BlockStore) (*Pool, e
 
 // PendingEvidence is used primarily as part of block proposal and returns up to maxNum of uncommitted evidence.
 // If maxNum is -1, all evidence is returned. Pending evidence is prioritised based on time.
-func (evpool *Pool) PendingEvidence(maxNum int64) []types.Evidence {
-	evidence, err := evpool.listEvidence(baseKeyPending, maxNum)
+func (evpool *Pool) PendingEvidence(maxNum uint32) []types.Evidence {
+	evidence, err := evpool.listEvidence(baseKeyPending, int64(maxNum))
+	if err != nil {
+		evpool.logger.Error("Unable to retrieve pending evidence", "err", err)
+	}
+	return evidence
+}
+
+func (evpool *Pool) AllPendingEvidence() []types.Evidence {
+	evidence, err := evpool.listEvidence(baseKeyPending, -1)
 	if err != nil {
 		evpool.logger.Error("Unable to retrieve pending evidence", "err", err)
 	}
@@ -300,7 +308,6 @@ func (evpool *Pool) removePendingEvidence(evidence types.Evidence) {
 }
 
 // listEvidence lists up to maxNum pieces of evidence for the given prefix key.
-// It is wrapped by PriorityEvidence and PendingEvidence for convenience.
 // If maxNum is -1, there's no cap on the size of returned evidence.
 func (evpool *Pool) listEvidence(prefixKey byte, maxNum int64) ([]types.Evidence, error) {
 	var count int64
diff --git a/evidence/pool_test.go b/evidence/pool_test.go
index a2f26cf98..dfbd7a429 100644
--- a/evidence/pool_test.go
+++ b/evidence/pool_test.go
@@ -96,7 +96,7 @@ func TestProposingAndCommittingEvidence(t *testing.T) {
 	assert.False(t, pool.IsCommitted(evidence))
 
 	// test evidence is proposed
-	proposedEvidence := pool.PendingEvidence(-1)
+	proposedEvidence := pool.AllPendingEvidence()
 	assert.Equal(t, proposedEvidence[0], evidence)
 
 	// evidence seen and committed:
diff --git a/evidence/reactor_test.go b/evidence/reactor_test.go
index eeedae2d1..09fc9fca7 100644
--- a/evidence/reactor_test.go
+++ b/evidence/reactor_test.go
@@ -92,11 +92,11 @@ func _waitForEvidence(
 	reactors []*Reactor,
 ) {
 	evpool := reactors[reactorIdx].evpool
-	for len(evpool.PendingEvidence(-1)) != len(evs) {
+	for len(evpool.AllPendingEvidence()) != len(evs) {
 		time.Sleep(time.Millisecond * 100)
 	}
 
-	reapedEv := evpool.PendingEvidence(-1)
+	reapedEv := evpool.AllPendingEvidence()
 	// put the reaped evidence in a map so we can quickly check we got everything
 	evMap := make(map[string]types.Evidence)
 	for _, e := range reapedEv {
diff --git a/node/node_test.go b/node/node_test.go
index ef21e3094..cb8f62752 100644
--- a/node/node_test.go
+++ b/node/node_test.go
@@ -219,6 +219,8 @@ func testFreeAddr(t *testing.T) string {
 // create a proposal block using real and full
 // mempool and evidence pool and validate it.
 func TestCreateProposalBlock(t *testing.T) {
+	const minEvSize = 12
+
 	config := cfg.ResetTestRoot("node_create_proposal")
 	defer os.RemoveAll(config.RootDir)
 	cc := proxy.NewLocalClientCreator(kvstore.NewApplication())
@@ -232,7 +234,9 @@ func TestCreateProposalBlock(t *testing.T) {
 	var height int64 = 1
 	state, stateDB := state(1, height)
 	maxBytes := 16384
+	maxEvidence := 10
 	state.ConsensusParams.Block.MaxBytes = int64(maxBytes)
+	state.ConsensusParams.Evidence.MaxNum = uint32(maxEvidence)
 	proposerAddr, _ := state.Validators.GetByIndex(0)
 
 	// Make Mempool
@@ -258,10 +262,8 @@ func TestCreateProposalBlock(t *testing.T) {
 
 	// fill the evidence pool with more evidence
 	// than can fit in a block
-	minEvSize := 12
-	numEv := (maxBytes / types.MaxEvidenceBytesDenominator) / minEvSize
-	for i := 0; i < numEv; i++ {
-		ev := types.NewMockRandomEvidence(1, time.Now(), proposerAddr, tmrand.Bytes(minEvSize))
+	for i := 0; i < maxEvidence+1; i++ {
+		ev := types.NewMockRandomEvidence(height, time.Now(), proposerAddr, tmrand.Bytes(minEvSize))
 		err := evidencePool.AddEvidence(ev)
 		require.NoError(t, err)
 	}
diff --git a/proto/types/params.pb.go b/proto/types/params.pb.go
index 359a8e346..ad1839122 100644
--- a/proto/types/params.pb.go
+++ b/proto/types/params.pb.go
@@ -146,6 +146,7 @@ type EvidenceParams struct {
 	// Note: must be greater than 0
 	MaxAgeNumBlocks      int64         `protobuf:"varint,1,opt,name=max_age_num_blocks,json=maxAgeNumBlocks,proto3" json:"max_age_num_blocks,omitempty"`
 	MaxAgeDuration       time.Duration `protobuf:"bytes,2,opt,name=max_age_duration,json=maxAgeDuration,proto3,stdduration" json:"max_age_duration"`
+	MaxNumEvidence       uint32        `protobuf:"varint,1,opt,name=max_num_evidence,json=maxNumEvidence,proto3" json:"max_num_evidence,omitempty"`
 	XXX_NoUnkeyedLiteral struct{}      `json:"-"`
 	XXX_unrecognized     []byte        `json:"-"`
 	XXX_sizecache        int32         `json:"-"`
@@ -189,6 +190,13 @@ func (m *EvidenceParams) GetMaxAgeDuration() time.Duration {
 	return 0
 }
 
+func (m *EvidenceParams) GetMaxNumEvidence() uint32 {
+	if m != nil {
+		return m.MaxNumEvidence
+	}
+	return 0
+}
+
 // ValidatorParams restrict the public key types validators can use.
 // NOTE: uses ABCI pubkey naming, not Amino names.
 type ValidatorParams struct {
diff --git a/proto/types/params.proto b/proto/types/params.proto
index b55246f1c..4e1b1f972 100644
--- a/proto/types/params.proto
+++ b/proto/types/params.proto
@@ -33,6 +33,7 @@ message EvidenceParams {
   int64                    max_age_num_blocks = 1;
   google.protobuf.Duration max_age_duration   = 2
       [(gogoproto.nullable) = false, (gogoproto.stdduration) = true];
+  uint32                   max_num            = 3;
 }
 
 // ValidatorParams restrict the public key types validators can use.
diff --git a/state/execution.go b/state/execution.go
index cd45484ce..038379b78 100644
--- a/state/execution.go
+++ b/state/execution.go
@@ -98,9 +98,7 @@ func (blockExec *BlockExecutor) CreateProposalBlock(
 	maxBytes := state.ConsensusParams.Block.MaxBytes
 	maxGas := state.ConsensusParams.Block.MaxGas
 
-	// Fetch a limited amount of valid evidence
-	maxNumEvidence, _ := types.MaxEvidencePerBlock(maxBytes)
-	evidence := blockExec.evpool.PendingEvidence(maxNumEvidence)
+	evidence := blockExec.evpool.PendingEvidence(state.ConsensusParams.Evidence.MaxNum)
 
 	// Fetch a limited amount of valid txs
 	maxDataBytes := types.MaxDataBytes(maxBytes, state.Validators.Size(), len(evidence))
diff --git a/state/mocks/evidence_pool.go b/state/mocks/evidence_pool.go
index 7100b2759..e3fe4a032 100644
--- a/state/mocks/evidence_pool.go
+++ b/state/mocks/evidence_pool.go
@@ -57,11 +57,11 @@ func (_m *EvidencePool) IsPending(_a0 types.Evidence) bool {
 }
 
 // PendingEvidence provides a mock function with given fields: _a0
-func (_m *EvidencePool) PendingEvidence(_a0 int64) []types.Evidence {
+func (_m *EvidencePool) PendingEvidence(_a0 uint32) []types.Evidence {
 	ret := _m.Called(_a0)
 
 	var r0 []types.Evidence
-	if rf, ok := ret.Get(0).(func(int64) []types.Evidence); ok {
+	if rf, ok := ret.Get(0).(func(uint32) []types.Evidence); ok {
 		r0 = rf(_a0)
 	} else {
 		if ret.Get(0) != nil {
diff --git a/state/services.go b/state/services.go
index 1eb40828c..6bd06de01 100644
--- a/state/services.go
+++ b/state/services.go
@@ -40,17 +40,18 @@ type BlockStore interface {
 // EvidencePool defines the EvidencePool interface used by the ConsensusState.
 // Get/Set/Commit
 type EvidencePool interface {
-	PendingEvidence(int64) []types.Evidence
+	PendingEvidence(uint32) []types.Evidence
 	AddEvidence(types.Evidence) error
 	Update(*types.Block, State)
 	IsCommitted(types.Evidence) bool
 	IsPending(types.Evidence) bool
 }
 
+// MockEvidencePool is an empty implementation of EvidencePool, useful for testing.
 type MockEvidencePool struct{}
 
-func (me MockEvidencePool) PendingEvidence(int64) []types.Evidence { return nil }
-func (me MockEvidencePool) AddEvidence(types.Evidence) error       { return nil }
-func (me MockEvidencePool) Update(*types.Block, State)             {}
-func (me MockEvidencePool) IsCommitted(types.Evidence) bool        { return false }
-func (me MockEvidencePool) IsPending(types.Evidence) bool          { return false }
+func (me MockEvidencePool) PendingEvidence(uint32) []types.Evidence { return nil }
+func (me MockEvidencePool) AddEvidence(types.Evidence) error        { return nil }
+func (me MockEvidencePool) Update(*types.Block, State)              {}
+func (me MockEvidencePool) IsCommitted(types.Evidence) bool         { return false }
+func (me MockEvidencePool) IsPending(types.Evidence) bool           { return false }
diff --git a/state/tx_filter.go b/state/tx_filter.go
index a8c0627dc..0754be3b1 100644
--- a/state/tx_filter.go
+++ b/state/tx_filter.go
@@ -11,6 +11,7 @@ func TxPreCheck(state State) mempl.PreCheckFunc {
 	maxDataBytes := types.MaxDataBytesUnknownEvidence(
 		state.ConsensusParams.Block.MaxBytes,
 		state.Validators.Size(),
+		state.ConsensusParams.Evidence.MaxNum,
 	)
 	return mempl.PreCheckAminoMaxBytes(maxDataBytes)
 }
diff --git a/state/tx_filter_test.go b/state/tx_filter_test.go
index 2dac856bd..ed1c8a402 100644
--- a/state/tx_filter_test.go
+++ b/state/tx_filter_test.go
@@ -17,6 +17,7 @@ import (
 func TestTxFilter(t *testing.T) {
 	genDoc := randomGenesisDoc()
 	genDoc.ConsensusParams.Block.MaxBytes = 3000
+	genDoc.ConsensusParams.Evidence.MaxNum = 1
 
 	// Max size of Txs is much smaller than size of block,
 	// since we need to account for commits and evidence.
@@ -24,10 +25,7 @@ func TestTxFilter(t *testing.T) {
 		tx    types.Tx
 		isErr bool
 	}{
-		{types.Tx(tmrand.Bytes(250)), false},
-		{types.Tx(tmrand.Bytes(1811)), false},
-		{types.Tx(tmrand.Bytes(1831)), false},
-		{types.Tx(tmrand.Bytes(1838)), true},
+		{types.Tx(tmrand.Bytes(1680)), false},
 		{types.Tx(tmrand.Bytes(1839)), true},
 		{types.Tx(tmrand.Bytes(3000)), true},
 	}
diff --git a/state/validation.go b/state/validation.go
index 6d2a7eb4d..ba8c22e95 100644
--- a/state/validation.go
+++ b/state/validation.go
@@ -120,11 +120,10 @@ func validateBlock(evidencePool EvidencePool, stateDB dbm.DB, state State, block
 	}
 
 	// Limit the amount of evidence
-	maxNumEvidence, _ := types.MaxEvidencePerBlock(state.ConsensusParams.Block.MaxBytes)
-	numEvidence := int64(len(block.Evidence.Evidence))
-	if numEvidence > maxNumEvidence {
-		return types.NewErrEvidenceOverflow(maxNumEvidence, numEvidence)
-
+	numEvidence := len(block.Evidence.Evidence)
+	// MaxNumEvidence is capped at uint16, so conversion is always safe.
+	if maxEvidence := int(state.ConsensusParams.Evidence.MaxNum); numEvidence > maxEvidence {
+		return types.NewErrEvidenceOverflow(maxEvidence, numEvidence)
 	}
 
 	// Validate all evidence.
diff --git a/state/validation_test.go b/state/validation_test.go
index 97a879156..640aa8ba3 100644
--- a/state/validation_test.go
+++ b/state/validation_test.go
@@ -216,16 +216,15 @@ func TestValidateBlockEvidence(t *testing.T) {
 	for height := int64(1); height < validationTestsStopHeight; height++ {
 		proposerAddr := state.Validators.GetProposer().Address
 		goodEvidence := types.NewMockEvidence(height, time.Now(), proposerAddr)
+		maxNumEvidence := state.ConsensusParams.Evidence.MaxNum
 		if height > 1 {
 			/*
 				A block with too much evidence fails
 			*/
-			maxBlockSize := state.ConsensusParams.Block.MaxBytes
-			maxNumEvidence, _ := types.MaxEvidencePerBlock(maxBlockSize)
 			require.True(t, maxNumEvidence > 2)
 			evidence := make([]types.Evidence, 0)
 			// one more than the maximum allowed evidence
-			for i := int64(0); i <= maxNumEvidence; i++ {
+			for i := uint32(0); i <= maxNumEvidence; i++ {
 				evidence = append(evidence, goodEvidence)
 			}
 			block, _ := state.MakeBlock(height, makeTxs(height), lastCommit, evidence, proposerAddr)
@@ -237,12 +236,10 @@ func TestValidateBlockEvidence(t *testing.T) {
 		/*
 			A good block with several pieces of good evidence passes
 		*/
-		maxBlockSize := state.ConsensusParams.Block.MaxBytes
-		maxNumEvidence, _ := types.MaxEvidencePerBlock(maxBlockSize)
 		require.True(t, maxNumEvidence > 2)
 		evidence := make([]types.Evidence, 0)
 		// precisely the amount of allowed evidence
-		for i := int64(0); i < maxNumEvidence; i++ {
+		for i := uint32(0); i < maxNumEvidence; i++ {
 			evidence = append(evidence, goodEvidence)
 		}
 
diff --git a/tools/tm-signer-harness/internal/test_harness_test.go b/tools/tm-signer-harness/internal/test_harness_test.go
index aebd9e341..632bc79ea 100644
--- a/tools/tm-signer-harness/internal/test_harness_test.go
+++ b/tools/tm-signer-harness/internal/test_harness_test.go
@@ -47,7 +47,8 @@ const (
 		},
 		"evidence": {
 			"max_age_num_blocks": "100000",
-			"max_age_duration": "172800000000000"
+			"max_age_duration": "172800000000000",
+			"max_num_evidence": 50
 		},
 		"validator": {
 			"pub_key_types": [
diff --git a/types/block.go b/types/block.go
index 7e112e5e5..5e08f4e7a 100644
--- a/types/block.go
+++ b/types/block.go
@@ -253,8 +253,8 @@ func MaxDataBytes(maxBytes int64, valsCount, evidenceCount int) int64 {
 // of evidence.
 //
 // XXX: Panics on negative result.
-func MaxDataBytesUnknownEvidence(maxBytes int64, valsCount int) int64 {
-	_, maxEvidenceBytes := MaxEvidencePerBlock(maxBytes)
+func MaxDataBytesUnknownEvidence(maxBytes int64, valsCount int, maxNumEvidence uint32) int64 {
+	maxEvidenceBytes := int64(maxNumEvidence) * MaxEvidenceBytes
 	maxDataBytes := maxBytes -
 		MaxAminoOverheadForBlock -
 		MaxHeaderBytes -
diff --git a/types/block_test.go b/types/block_test.go
index 36eb0b146..00cca535e 100644
--- a/types/block_test.go
+++ b/types/block_test.go
@@ -399,28 +399,30 @@ func TestBlockMaxDataBytes(t *testing.T) {
 
 func TestBlockMaxDataBytesUnknownEvidence(t *testing.T) {
 	testCases := []struct {
-		maxBytes  int64
-		valsCount int
-		panics    bool
-		result    int64
+		maxBytes    int64
+		maxEvidence uint32
+		valsCount   int
+		panics      bool
+		result      int64
 	}{
-		0: {-10, 1, true, 0},
-		1: {10, 1, true, 0},
-		2: {961, 1, true, 0},
-		3: {962, 1, false, 0},
-		4: {963, 1, false, 1},
+		0: {-10, 0, 1, true, 0},
+		1: {10, 0, 1, true, 0},
+		2: {865, 0, 1, true, 0},
+		3: {866, 0, 1, false, 0},
+		4: {1310, 1, 1, false, 0},
+		5: {1311, 1, 1, false, 1},
 	}
 
 	for i, tc := range testCases {
 		tc := tc
 		if tc.panics {
 			assert.Panics(t, func() {
-				MaxDataBytesUnknownEvidence(tc.maxBytes, tc.valsCount)
+				MaxDataBytesUnknownEvidence(tc.maxBytes, tc.valsCount, tc.maxEvidence)
 			}, "#%v", i)
 		} else {
 			assert.Equal(t,
 				tc.result,
-				MaxDataBytesUnknownEvidence(tc.maxBytes, tc.valsCount),
+				MaxDataBytesUnknownEvidence(tc.maxBytes, tc.valsCount, tc.maxEvidence),
 				"#%v", i)
 		}
 	}
diff --git a/types/evidence.go b/types/evidence.go
index 8fe7ab80e..84c31dd98 100644
--- a/types/evidence.go
+++ b/types/evidence.go
@@ -48,12 +48,12 @@ func (err *ErrEvidenceInvalid) Error() string {
 
 // ErrEvidenceOverflow is for when there is too much evidence in a block.
 type ErrEvidenceOverflow struct {
-	MaxNum int64
-	GotNum int64
+	MaxNum int
+	GotNum int
 }
 
 // NewErrEvidenceOverflow returns a new ErrEvidenceOverflow where got > max.
-func NewErrEvidenceOverflow(max, got int64) *ErrEvidenceOverflow {
+func NewErrEvidenceOverflow(max, got int) *ErrEvidenceOverflow {
 	return &ErrEvidenceOverflow{max, got}
 }
 
@@ -97,21 +97,6 @@ func RegisterMockEvidences(cdc *amino.Codec) {
 	cdc.RegisterConcrete(MockRandomEvidence{}, "tendermint/MockRandomEvidence", nil)
 }
 
-const (
-	MaxEvidenceBytesDenominator = 10
-)
-
-// MaxEvidencePerBlock returns the maximum number of evidences
-// allowed in the block and their maximum total size (limitted to 1/10th
-// of the maximum block size).
-// TODO: change to a constant, or to a fraction of the validator set size.
-// See https://github.com/tendermint/tendermint/issues/2590
-func MaxEvidencePerBlock(blockMaxBytes int64) (int64, int64) {
-	maxBytes := blockMaxBytes / MaxEvidenceBytesDenominator
-	maxNum := maxBytes / MaxEvidenceBytes
-	return maxNum, maxBytes
-}
-
 //-------------------------------------------
 
 // DuplicateVoteEvidence contains evidence a validator signed two conflicting
diff --git a/types/params.go b/types/params.go
index d84441b84..82a16942b 100644
--- a/types/params.go
+++ b/types/params.go
@@ -19,6 +19,9 @@ const (
 
 	// MaxBlockPartsCount is the maximum number of block parts.
 	MaxBlockPartsCount = (MaxBlockSizeBytes / BlockPartSizeBytes) + 1
+
+	// Restrict the upper bound of the amount of evidence (uses uint16 for safe conversion)
+	MaxEvidencePerBlock = 65535
 )
 
 // ConsensusParams contains consensus critical parameters that determine the
@@ -67,6 +70,12 @@ type EvidenceParams struct {
 	// mechanism for handling [Nothing-At-Stake
 	// attacks](https://github.com/ethereum/wiki/wiki/Proof-of-Stake-FAQ#what-is-the-nothing-at-stake-problem-and-how-can-it-be-fixed).
 	MaxAgeDuration time.Duration `json:"max_age_duration"`
+
+	// This sets the maximum number of evidence that can be committed in a single block.
+	// and should fall comfortably under the max block bytes when we consider the size of
+	// each evidence (See MaxEvidenceBytes). The maximum number is MaxEvidencePerBlock.
+	// Default is 50
+	MaxNum uint32 `json:"max_num"`
 }
 
 // ValidatorParams restrict the public key types validators can use.
@@ -98,6 +107,7 @@ func DefaultEvidenceParams() EvidenceParams {
 	return EvidenceParams{
 		MaxAgeNumBlocks: 100000, // 27.8 hrs at 1block/s
 		MaxAgeDuration:  48 * time.Hour,
+		MaxNum:          50,
 	}
 }
 
@@ -148,6 +158,16 @@ func (params *ConsensusParams) Validate() error {
 			params.Evidence.MaxAgeDuration)
 	}
 
+	if params.Evidence.MaxNum > MaxEvidencePerBlock {
+		return errors.Errorf("evidenceParams.MaxNumEvidence is greater than upper bound, %d > %d",
+			params.Evidence.MaxNum, MaxEvidencePerBlock)
+	}
+
+	if int64(params.Evidence.MaxNum)*MaxEvidenceBytes > params.Block.MaxBytes {
+		return errors.Errorf("total possible evidence size is bigger than block.MaxBytes, %d > %d",
+			int64(params.Evidence.MaxNum)*MaxEvidenceBytes, params.Block.MaxBytes)
+	}
+
 	if len(params.Validator.PubKeyTypes) == 0 {
 		return errors.New("len(Validator.PubKeyTypes) must be greater than 0")
 	}
@@ -204,6 +224,7 @@ func (params ConsensusParams) Update(params2 *abci.ConsensusParams) ConsensusPar
 	if params2.Evidence != nil {
 		res.Evidence.MaxAgeNumBlocks = params2.Evidence.MaxAgeNumBlocks
 		res.Evidence.MaxAgeDuration = params2.Evidence.MaxAgeDuration
+		res.Evidence.MaxNum = params2.Evidence.MaxNumEvidence
 	}
 	if params2.Validator != nil {
 		// Copy params2.Validator.PubkeyTypes, and set result's value to the copy.
diff --git a/types/params_test.go b/types/params_test.go
index b446bda33..dc3a3cf0a 100644
--- a/types/params_test.go
+++ b/types/params_test.go
@@ -22,22 +22,24 @@ func TestConsensusParamsValidation(t *testing.T) {
 		valid  bool
 	}{
 		// test block params
-		0: {makeParams(1, 0, 10, 1, valEd25519), true},
-		1: {makeParams(0, 0, 10, 1, valEd25519), false},
-		2: {makeParams(47*1024*1024, 0, 10, 1, valEd25519), true},
-		3: {makeParams(10, 0, 10, 1, valEd25519), true},
-		4: {makeParams(100*1024*1024, 0, 10, 1, valEd25519), true},
-		5: {makeParams(101*1024*1024, 0, 10, 1, valEd25519), false},
-		6: {makeParams(1024*1024*1024, 0, 10, 1, valEd25519), false},
-		7: {makeParams(1024*1024*1024, 0, 10, -1, valEd25519), false},
-		8: {makeParams(1, 0, -10, 1, valEd25519), false},
+		0: {makeParams(1, 0, 10, 1, 0, valEd25519), true},
+		1: {makeParams(0, 0, 10, 1, 0, valEd25519), false},
+		2: {makeParams(47*1024*1024, 0, 10, 1, 0, valEd25519), true},
+		3: {makeParams(10, 0, 10, 1, 0, valEd25519), true},
+		4: {makeParams(100*1024*1024, 0, 10, 1, 0, valEd25519), true},
+		5: {makeParams(101*1024*1024, 0, 10, 1, 0, valEd25519), false},
+		6: {makeParams(1024*1024*1024, 0, 10, 1, 0, valEd25519), false},
+		7: {makeParams(1024*1024*1024, 0, 10, -1, 0, valEd25519), false},
+		8: {makeParams(1, 0, -10, 1, 0, valEd25519), false},
 		// test evidence params
-		9:  {makeParams(1, 0, 10, 0, valEd25519), false},
-		10: {makeParams(1, 0, 10, -1, valEd25519), false},
+		9:  {makeParams(1, 0, 10, 0, 0, valEd25519), false},
+		10: {makeParams(1, 0, 10, 1, 1, valEd25519), false},
+		11: {makeParams(1000, 0, 10, 1, 1, valEd25519), true},
+		12: {makeParams(1, 0, 10, -1, 0, valEd25519), false},
 		// test no pubkey type provided
-		11: {makeParams(1, 0, 10, 1, []string{}), false},
+		13: {makeParams(1, 0, 10, 1, 0, []string{}), false},
 		// test invalid pubkey type provided
-		12: {makeParams(1, 0, 10, 1, []string{"potatoes make good pubkeys"}), false},
+		14: {makeParams(1, 0, 10, 1, 0, []string{"potatoes make good pubkeys"}), false},
 	}
 	for i, tc := range testCases {
 		if tc.valid {
@@ -52,6 +54,7 @@ func makeParams(
 	blockBytes, blockGas int64,
 	blockTimeIotaMs int64,
 	evidenceAge int64,
+	maxEvidence uint32,
 	pubkeyTypes []string,
 ) ConsensusParams {
 	return ConsensusParams{
@@ -63,6 +66,7 @@ func makeParams(
 		Evidence: EvidenceParams{
 			MaxAgeNumBlocks: evidenceAge,
 			MaxAgeDuration:  time.Duration(evidenceAge),
+			MaxNum:          maxEvidence,
 		},
 		Validator: ValidatorParams{
 			PubKeyTypes: pubkeyTypes,
@@ -72,14 +76,14 @@ func makeParams(
 
 func TestConsensusParamsHash(t *testing.T) {
 	params := []ConsensusParams{
-		makeParams(4, 2, 10, 3, valEd25519),
-		makeParams(1, 4, 10, 3, valEd25519),
-		makeParams(1, 2, 10, 4, valEd25519),
-		makeParams(2, 5, 10, 7, valEd25519),
-		makeParams(1, 7, 10, 6, valEd25519),
-		makeParams(9, 5, 10, 4, valEd25519),
-		makeParams(7, 8, 10, 9, valEd25519),
-		makeParams(4, 6, 10, 5, valEd25519),
+		makeParams(4, 2, 10, 3, 1, valEd25519),
+		makeParams(1, 4, 10, 3, 1, valEd25519),
+		makeParams(1, 2, 10, 4, 1, valEd25519),
+		makeParams(2, 5, 10, 7, 1, valEd25519),
+		makeParams(1, 7, 10, 6, 1, valEd25519),
+		makeParams(9, 5, 10, 4, 1, valEd25519),
+		makeParams(7, 8, 10, 9, 1, valEd25519),
+		makeParams(4, 6, 10, 5, 1, valEd25519),
 	}
 
 	hashes := make([][]byte, len(params))
@@ -105,13 +109,13 @@ func TestConsensusParamsUpdate(t *testing.T) {
 	}{
 		// empty updates
 		{
-			makeParams(1, 2, 10, 3, valEd25519),
+			makeParams(1, 2, 10, 3, 0, valEd25519),
 			&abci.ConsensusParams{},
-			makeParams(1, 2, 10, 3, valEd25519),
+			makeParams(1, 2, 10, 3, 0, valEd25519),
 		},
 		// fine updates
 		{
-			makeParams(1, 2, 10, 3, valEd25519),
+			makeParams(1, 2, 10, 3, 0, valEd25519),
 			&abci.ConsensusParams{
 				Block: &abci.BlockParams{
 					MaxBytes: 100,
@@ -120,12 +124,13 @@ func TestConsensusParamsUpdate(t *testing.T) {
 				Evidence: &abci.EvidenceParams{
 					MaxAgeNumBlocks: 300,
 					MaxAgeDuration:  time.Duration(300),
+					MaxNumEvidence:  50,
 				},
 				Validator: &abci.ValidatorParams{
 					PubKeyTypes: valSecp256k1,
 				},
 			},
-			makeParams(100, 200, 10, 300, valSecp256k1),
+			makeParams(100, 200, 10, 300, 50, valSecp256k1),
 		},
 	}
 	for _, tc := range testCases {
diff --git a/types/protobuf.go b/types/protobuf.go
index a185722f1..bc15d914d 100644
--- a/types/protobuf.go
+++ b/types/protobuf.go
@@ -139,6 +139,7 @@ func (tm2pb) ConsensusParams(params *ConsensusParams) *abci.ConsensusParams {
 		Evidence: &abci.EvidenceParams{
 			MaxAgeNumBlocks: params.Evidence.MaxAgeNumBlocks,
 			MaxAgeDuration:  params.Evidence.MaxAgeDuration,
+			MaxNumEvidence:  params.Evidence.MaxNum,
 		},
 		Validator: &abci.ValidatorParams{
 			PubKeyTypes: params.Validator.PubKeyTypes,