diff --git a/backend/azure/azure.go b/backend/azure/azure.go
index 282525b..c8a7781 100644
--- a/backend/azure/azure.go
+++ b/backend/azure/azure.go
@@ -1041,10 +1041,10 @@ func (az *Azure) CreateMultipartUpload(ctx context.Context, input s3response.Cre
 		for _, prt := range tagParts {
 			p := strings.Split(prt, "=")
 			if len(p) != 2 {
-				return s3response.InitiateMultipartUploadResult{}, s3err.GetAPIError(s3err.ErrInvalidTag)
+				return s3response.InitiateMultipartUploadResult{}, s3err.GetAPIError(s3err.ErrInvalidTagValue)
 			}
 			if len(p[0]) > 128 || len(p[1]) > 256 {
-				return s3response.InitiateMultipartUploadResult{}, s3err.GetAPIError(s3err.ErrInvalidTag)
+				return s3response.InitiateMultipartUploadResult{}, s3err.GetAPIError(s3err.ErrInvalidTagValue)
 			}
 			tags[p[0]] = p[1]
 		}
@@ -1827,7 +1827,7 @@ func parseTags(tagstr *string) (map[string]string, error) {
 		for _, prt := range tagParts {
 			p := strings.Split(prt, "=")
 			if len(p) != 2 {
-				return nil, s3err.GetAPIError(s3err.ErrInvalidTag)
+				return nil, s3err.GetAPIError(s3err.ErrInvalidTagValue)
 			}
 			tags[p[0]] = p[1]
 		}
diff --git a/backend/azure/err.go b/backend/azure/err.go
index 0300702..932209e 100644
--- a/backend/azure/err.go
+++ b/backend/azure/err.go
@@ -40,7 +40,7 @@ func azErrToS3err(azErr *azcore.ResponseError) s3err.APIError {
 	case "BlobNotFound":
 		return s3err.GetAPIError(s3err.ErrNoSuchKey)
 	case "TagsTooLarge":
-		return s3err.GetAPIError(s3err.ErrInvalidTag)
+		return s3err.GetAPIError(s3err.ErrInvalidTagValue)
 	case "Requested Range Not Satisfiable":
 		return s3err.GetAPIError(s3err.ErrInvalidRange)
 	}
diff --git a/backend/common.go b/backend/common.go
index 8a461a4..36f4fc7 100644
--- a/backend/common.go
+++ b/backend/common.go
@@ -227,10 +227,10 @@ func ParseObjectTags(t string) (map[string]string, error) {
 	for _, prt := range tagParts {
 		p := strings.Split(prt, "=")
 		if len(p) != 2 {
-			return nil, s3err.GetAPIError(s3err.ErrInvalidTag)
+			return nil, s3err.GetAPIError(s3err.ErrInvalidTagValue)
 		}
 		if len(p[0]) > 128 || len(p[1]) > 256 {
-			return nil, s3err.GetAPIError(s3err.ErrInvalidTag)
+			return nil, s3err.GetAPIError(s3err.ErrInvalidTagValue)
 		}
 		tagging[p[0]] = p[1]
 	}
diff --git a/s3api/controllers/base.go b/s3api/controllers/base.go
index 0666f28..8f3ba30 100644
--- a/s3api/controllers/base.go
+++ b/s3api/controllers/base.go
@@ -1211,13 +1211,9 @@ func (c S3ApiController) PutBucketActions(ctx *fiber.Ctx) error {
 	if ctx.Request().URI().QueryArgs().Has("tagging") {
 		parsedAcl := ctx.Locals("parsedAcl").(auth.ACL)
 
-		var bucketTagging s3response.TaggingInput
-		err := xml.Unmarshal(ctx.Body(), &bucketTagging)
+		tagging, err := utils.ParseTagging(ctx.Body(), utils.TagLimitBucket, c.debug)
 		if err != nil {
-			if c.debug {
-				debuglogger.Logf("error unmarshalling bucket tagging: %v", err)
-			}
-			return SendResponse(ctx, s3err.GetAPIError(s3err.ErrInvalidRequest),
+			return SendResponse(ctx, err,
 				&MetaOpts{
 					Logger:      c.logger,
 					MetricsMng:  c.mm,
@@ -1226,37 +1222,6 @@ func (c S3ApiController) PutBucketActions(ctx *fiber.Ctx) error {
 				})
 		}
 
-		if len(bucketTagging.TagSet.Tags) > 50 {
-			if c.debug {
-				debuglogger.Logf("bucket tagging length exceeds 50: %v", len(bucketTagging.TagSet.Tags))
-			}
-			return SendResponse(ctx, s3err.GetAPIError(s3err.ErrBucketTaggingLimited),
-				&MetaOpts{
-					Logger:      c.logger,
-					MetricsMng:  c.mm,
-					Action:      metrics.ActionPutBucketTagging,
-					BucketOwner: parsedAcl.Owner,
-				})
-		}
-
-		tags := make(map[string]string, len(bucketTagging.TagSet.Tags))
-
-		for _, tag := range bucketTagging.TagSet.Tags {
-			if len(tag.Key) > 128 || len(tag.Value) > 256 {
-				if c.debug {
-					debuglogger.Logf("invalid long bucket tagging key/value")
-				}
-				return SendResponse(ctx, s3err.GetAPIError(s3err.ErrInvalidTag),
-					&MetaOpts{
-						Logger:      c.logger,
-						MetricsMng:  c.mm,
-						Action:      metrics.ActionPutBucketTagging,
-						BucketOwner: parsedAcl.Owner,
-					})
-			}
-			tags[tag.Key] = tag.Value
-		}
-
 		err = auth.VerifyAccess(ctx.Context(), c.be, auth.AccessOptions{
 			Readonly:      c.readonly,
 			Acl:           parsedAcl,
@@ -1276,7 +1241,7 @@ func (c S3ApiController) PutBucketActions(ctx *fiber.Ctx) error {
 				})
 		}
 
-		err = c.be.PutBucketTagging(ctx.Context(), bucket, tags)
+		err = c.be.PutBucketTagging(ctx.Context(), bucket, tagging)
 		return SendResponse(ctx, err,
 			&MetaOpts{
 				Logger:      c.logger,
@@ -1873,13 +1838,9 @@ func (c S3ApiController) PutActions(ctx *fiber.Ctx) error {
 	}
 
 	if ctx.Request().URI().QueryArgs().Has("tagging") {
-		var objTagging s3response.TaggingInput
-		err := xml.Unmarshal(ctx.Body(), &objTagging)
+		tagging, err := utils.ParseTagging(ctx.Body(), utils.TagLimitObject, c.debug)
 		if err != nil {
-			if c.debug {
-				debuglogger.Logf("error unmarshalling object tagging: %v", err)
-			}
-			return SendResponse(ctx, s3err.GetAPIError(s3err.ErrInvalidRequest),
+			return SendResponse(ctx, err,
 				&MetaOpts{
 					Logger:      c.logger,
 					MetricsMng:  c.mm,
@@ -1888,38 +1849,6 @@ func (c S3ApiController) PutActions(ctx *fiber.Ctx) error {
 				})
 		}
 
-		if len(objTagging.TagSet.Tags) > 10 {
-			if c.debug {
-				debuglogger.Logf("bucket tagging length exceeds 10: %v", len(objTagging.TagSet.Tags))
-			}
-			return SendResponse(ctx, s3err.GetAPIError(s3err.ErrObjectTaggingLimited),
-				&MetaOpts{
-					Logger:      c.logger,
-					MetricsMng:  c.mm,
-					Action:      metrics.ActionPutObjectTagging,
-					BucketOwner: parsedAcl.Owner,
-				})
-		}
-
-		tags := make(map[string]string, len(objTagging.TagSet.Tags))
-
-		for _, tag := range objTagging.TagSet.Tags {
-			if len(tag.Key) > 128 || len(tag.Value) > 256 {
-				if c.debug {
-					debuglogger.Logf("invalid tag key/value len: %q %q",
-						tag.Key, tag.Value)
-				}
-				return SendResponse(ctx, s3err.GetAPIError(s3err.ErrInvalidTag),
-					&MetaOpts{
-						Logger:      c.logger,
-						MetricsMng:  c.mm,
-						Action:      metrics.ActionPutObjectTagging,
-						BucketOwner: parsedAcl.Owner,
-					})
-			}
-			tags[tag.Key] = tag.Value
-		}
-
 		err = auth.VerifyAccess(ctx.Context(), c.be, auth.AccessOptions{
 			Readonly:      c.readonly,
 			Acl:           parsedAcl,
@@ -1940,7 +1869,7 @@ func (c S3ApiController) PutActions(ctx *fiber.Ctx) error {
 				})
 		}
 
-		err = c.be.PutObjectTagging(ctx.Context(), bucket, keyStart, tags)
+		err = c.be.PutObjectTagging(ctx.Context(), bucket, keyStart, tagging)
 		return SendResponse(ctx, err,
 			&MetaOpts{
 				Logger:      c.logger,
diff --git a/s3api/utils/utils.go b/s3api/utils/utils.go
index a95d035..86e8856 100644
--- a/s3api/utils/utils.go
+++ b/s3api/utils/utils.go
@@ -17,6 +17,7 @@ package utils
 import (
 	"bytes"
 	"encoding/base64"
+	"encoding/xml"
 	"errors"
 	"fmt"
 	"io"
@@ -719,3 +720,74 @@ func ParseCreateMpChecksumHeaders(ctx *fiber.Ctx, debug bool) (types.ChecksumAlg
 
 	return algo, chType, nil
 }
+
+// TagLimit specifies the allowed tag count in a tag set
+type TagLimit int
+
+const (
+	// Tag limit for bucket tagging
+	TagLimitBucket TagLimit = 50
+	// Tag limit for object tagging
+	TagLimitObject TagLimit = 10
+)
+
+// Parses and validates tagging
+func ParseTagging(data []byte, limit TagLimit, debug bool) (map[string]string, error) {
+	var tagging s3response.TaggingInput
+	err := xml.Unmarshal(data, &tagging)
+	if err != nil {
+		if debug {
+			debuglogger.Logf("invalid taggging: %s", data)
+		}
+		return nil, s3err.GetAPIError(s3err.ErrMalformedXML)
+	}
+
+	tLen := len(tagging.TagSet.Tags)
+	if tLen > int(limit) {
+		switch limit {
+		case TagLimitObject:
+			if debug {
+				debuglogger.Logf("bucket tagging length exceeds %v: %v", limit, tLen)
+			}
+			return nil, s3err.GetAPIError(s3err.ErrObjectTaggingLimited)
+		case TagLimitBucket:
+			if debug {
+				debuglogger.Logf("object tagging length exceeds %v: %v", limit, tLen)
+			}
+			return nil, s3err.GetAPIError(s3err.ErrBucketTaggingLimited)
+		}
+	}
+
+	tagSet := make(map[string]string, tLen)
+
+	for _, tag := range tagging.TagSet.Tags {
+		// validate tag key
+		if len(tag.Key) == 0 || len(tag.Key) > 128 {
+			if debug {
+				debuglogger.Logf("tag key should 0 < tag.Key <= 128, key: %v", tag.Key)
+			}
+			return nil, s3err.GetAPIError(s3err.ErrInvalidTagKey)
+		}
+
+		// validate tag value
+		if len(tag.Value) > 256 {
+			if debug {
+				debuglogger.Logf("invalid long tag value: (length): %v, (value): %v", len(tag.Value), tag.Value)
+			}
+			return nil, s3err.GetAPIError(s3err.ErrInvalidTagValue)
+		}
+
+		// make sure there are no duplicate keys
+		_, ok := tagSet[tag.Key]
+		if ok {
+			if debug {
+				debuglogger.Logf("duplicate tag key: %v", tag.Key)
+			}
+			return nil, s3err.GetAPIError(s3err.ErrDuplicateTagKey)
+		}
+
+		tagSet[tag.Key] = tag.Value
+	}
+
+	return tagSet, nil
+}
diff --git a/s3api/utils/utils_test.go b/s3api/utils/utils_test.go
index 205115d..9db30f1 100644
--- a/s3api/utils/utils_test.go
+++ b/s3api/utils/utils_test.go
@@ -16,6 +16,9 @@ package utils
 
 import (
 	"bytes"
+	"encoding/xml"
+	"errors"
+	"math/rand"
 	"net/http"
 	"reflect"
 	"testing"
@@ -25,6 +28,7 @@ import (
 	"github.com/gofiber/fiber/v2"
 	"github.com/valyala/fasthttp"
 	"github.com/versity/versitygw/backend"
+	"github.com/versity/versitygw/s3err"
 	"github.com/versity/versitygw/s3response"
 )
 
@@ -857,3 +861,163 @@ func Test_checkChecksumTypeAndAlgo(t *testing.T) {
 		})
 	}
 }
+
+func TestParseTagging(t *testing.T) {
+	genRandStr := func(lgth int) string {
+		b := make([]byte, lgth)
+		for i := range b {
+			b[i] = byte(rand.Intn(95) + 32) // 126 - 32 + 1 = 95 printable characters
+		}
+		return string(b)
+	}
+	getTagSet := func(lgth int) s3response.TaggingInput {
+		res := s3response.TaggingInput{
+			TagSet: s3response.TagSet{
+				Tags: []s3response.Tag{},
+			},
+		}
+
+		for i := 0; i < lgth; i++ {
+			res.TagSet.Tags = append(res.TagSet.Tags, s3response.Tag{
+				Key:   genRandStr(10),
+				Value: genRandStr(20),
+			})
+		}
+
+		return res
+	}
+	type args struct {
+		data        s3response.TaggingInput
+		overrideXML []byte
+		limit       TagLimit
+		debug       bool
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    map[string]string
+		wantErr error
+	}{
+		{
+			name: "valid tags within limit",
+			args: args{
+				data: s3response.TaggingInput{
+					TagSet: s3response.TagSet{
+						Tags: []s3response.Tag{
+							{Key: "key1", Value: "value1"},
+							{Key: "key2", Value: "value2"},
+						},
+					},
+				},
+				limit: TagLimitObject,
+			},
+			want:    map[string]string{"key1": "value1", "key2": "value2"},
+			wantErr: nil,
+		},
+		{
+			name: "malformed XML",
+			args: args{
+				overrideXML: []byte("invalid xml"),
+				limit:       TagLimitObject,
+			},
+			want:    nil,
+			wantErr: s3err.GetAPIError(s3err.ErrMalformedXML),
+		},
+		{
+			name: "exceeds bucket tag limit",
+			args: args{
+				data:  getTagSet(51),
+				limit: TagLimitBucket,
+			},
+			want:    nil,
+			wantErr: s3err.GetAPIError(s3err.ErrBucketTaggingLimited),
+		},
+		{
+			name: "exceeds object tag limit",
+			args: args{
+				data:  getTagSet(11),
+				limit: TagLimitObject,
+			},
+			want:    nil,
+			wantErr: s3err.GetAPIError(s3err.ErrObjectTaggingLimited),
+		},
+		{
+			name: "invalid 0 length tag key",
+			args: args{
+				data: s3response.TaggingInput{
+					TagSet: s3response.TagSet{
+						Tags: []s3response.Tag{{Key: "", Value: "value1"}},
+					},
+				},
+				limit: TagLimitObject,
+			},
+			want:    nil,
+			wantErr: s3err.GetAPIError(s3err.ErrInvalidTagKey),
+		},
+		{
+			name: "invalid long tag key",
+			args: args{
+				data: s3response.TaggingInput{
+					TagSet: s3response.TagSet{
+						Tags: []s3response.Tag{{Key: genRandStr(130), Value: "value1"}},
+					},
+				},
+				limit: TagLimitObject,
+			},
+			want:    nil,
+			wantErr: s3err.GetAPIError(s3err.ErrInvalidTagKey),
+		},
+		{
+			name: "invalid long tag value",
+			args: args{
+				data: s3response.TaggingInput{
+					TagSet: s3response.TagSet{
+						Tags: []s3response.Tag{{Key: "key", Value: genRandStr(257)}},
+					},
+				},
+				limit: TagLimitBucket,
+			},
+			want:    nil,
+			wantErr: s3err.GetAPIError(s3err.ErrInvalidTagValue),
+		},
+		{
+			name: "duplicate tag key",
+			args: args{
+				data: s3response.TaggingInput{
+					TagSet: s3response.TagSet{
+						Tags: []s3response.Tag{
+							{Key: "key", Value: "value1"},
+							{Key: "key", Value: "value2"},
+						},
+					},
+				},
+				limit: TagLimitObject,
+			},
+			want:    nil,
+			wantErr: s3err.GetAPIError(s3err.ErrDuplicateTagKey),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var data []byte
+			if tt.args.overrideXML != nil {
+				data = tt.args.overrideXML
+			} else {
+				var err error
+				data, err = xml.Marshal(tt.args.data)
+				if err != nil {
+					t.Fatalf("error marshalling input: %v", err)
+				}
+			}
+			got, err := ParseTagging(data, tt.args.limit, tt.args.debug)
+
+			if !errors.Is(err, tt.wantErr) {
+				t.Errorf("expected error %v, got %v", tt.wantErr, err)
+			}
+			if err == nil && !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("expected result %v, got %v", tt.want, got)
+			}
+		})
+	}
+}
diff --git a/s3err/s3err.go b/s3err/s3err.go
index 82f8b99..a895285 100644
--- a/s3err/s3err.go
+++ b/s3err/s3err.go
@@ -84,7 +84,9 @@ const (
 	ErrInvalidCopyDest
 	ErrInvalidCopySource
 	ErrInvalidCopySourceRange
-	ErrInvalidTag
+	ErrInvalidTagKey
+	ErrInvalidTagValue
+	ErrDuplicateTagKey
 	ErrBucketTaggingLimited
 	ErrObjectTaggingLimited
 	ErrAuthHeaderEmpty
@@ -308,11 +310,21 @@ var errorCodeResponse = map[ErrorCode]APIError{
 		Description:    "The x-amz-copy-source-range value must be of the form bytes=first-last where first and last are the zero-based offsets of the first and last bytes to copy",
 		HTTPStatusCode: http.StatusBadRequest,
 	},
-	ErrInvalidTag: {
+	ErrInvalidTagKey: {
+		Code:           "InvalidTag",
+		Description:    "The TagKey you have provided is invalid",
+		HTTPStatusCode: http.StatusBadRequest,
+	},
+	ErrInvalidTagValue: {
 		Code:           "InvalidTag",
 		Description:    "The TagValue you have provided is invalid",
 		HTTPStatusCode: http.StatusBadRequest,
 	},
+	ErrDuplicateTagKey: {
+		Code:           "InvalidTag",
+		Description:    "Cannot provide multiple Tags with the same key",
+		HTTPStatusCode: http.StatusBadRequest,
+	},
 	ErrBucketTaggingLimited: {
 		Code:           "BadRequest",
 		Description:    "Bucket tag count cannot be greater than 50",
diff --git a/tests/integration/group-tests.go b/tests/integration/group-tests.go
index 1f46b57..93af571 100644
--- a/tests/integration/group-tests.go
+++ b/tests/integration/group-tests.go
@@ -118,6 +118,7 @@ func TestDeleteBucketOwnershipControls(s *S3Conf) {
 func TestPutBucketTagging(s *S3Conf) {
 	PutBucketTagging_non_existing_bucket(s)
 	PutBucketTagging_long_tags(s)
+	PutBucketTagging_duplicate_keys(s)
 	PutBucketTagging_tag_count_limit(s)
 	PutBucketTagging_success(s)
 	PutBucketTagging_success_status(s)
@@ -298,6 +299,7 @@ func TestCopyObject(s *S3Conf) {
 func TestPutObjectTagging(s *S3Conf) {
 	PutObjectTagging_non_existing_object(s)
 	PutObjectTagging_long_tags(s)
+	PutObjectTagging_duplicate_keys(s)
 	PutObjectTagging_tag_count_limit(s)
 	PutObjectTagging_success(s)
 }
@@ -852,6 +854,7 @@ func GetIntTests() IntTests {
 		"DeleteBucketOwnershipControls_success":                                   DeleteBucketOwnershipControls_success,
 		"PutBucketTagging_non_existing_bucket":                                    PutBucketTagging_non_existing_bucket,
 		"PutBucketTagging_long_tags":                                              PutBucketTagging_long_tags,
+		"PutBucketTagging_duplicate_keys":                                         PutBucketTagging_duplicate_keys,
 		"PutBucketTagging_tag_count_limit":                                        PutBucketTagging_tag_count_limit,
 		"PutBucketTagging_success":                                                PutBucketTagging_success,
 		"PutBucketTagging_success_status":                                         PutBucketTagging_success_status,
@@ -959,6 +962,7 @@ func GetIntTests() IntTests {
 		"CopyObject_success":                                                      CopyObject_success,
 		"PutObjectTagging_non_existing_object":                                    PutObjectTagging_non_existing_object,
 		"PutObjectTagging_long_tags":                                              PutObjectTagging_long_tags,
+		"PutObjectTagging_duplicate_keys":                                         PutObjectTagging_duplicate_keys,
 		"PutObjectTagging_tag_count_limit":                                        PutObjectTagging_tag_count_limit,
 		"PutObjectTagging_success":                                                PutObjectTagging_success,
 		"GetObjectTagging_non_existing_object":                                    GetObjectTagging_non_existing_object,
diff --git a/tests/integration/tests.go b/tests/integration/tests.go
index 6f634eb..914fda8 100644
--- a/tests/integration/tests.go
+++ b/tests/integration/tests.go
@@ -2500,7 +2500,7 @@ func PutBucketTagging_long_tags(s *S3Conf) error {
 			Bucket:  &bucket,
 			Tagging: &tagging})
 		cancel()
-		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTag)); err != nil {
+		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTagKey)); err != nil {
 			return err
 		}
 
@@ -2511,7 +2511,32 @@ func PutBucketTagging_long_tags(s *S3Conf) error {
 			Bucket:  &bucket,
 			Tagging: &tagging})
 		cancel()
-		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTag)); err != nil {
+		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTagValue)); err != nil {
+			return err
+		}
+
+		return nil
+	})
+}
+
+func PutBucketTagging_duplicate_keys(s *S3Conf) error {
+	testName := "PutBucketTagging_duplicate_keys"
+	return actionHandler(s, testName, func(s3client *s3.Client, bucket string) error {
+		tagging := types.Tagging{
+			TagSet: []types.Tag{
+				{Key: getPtr("key"), Value: getPtr("value")},
+				{Key: getPtr("key"), Value: getPtr("value-1")},
+				{Key: getPtr("key-1"), Value: getPtr("value-2")},
+				{Key: getPtr("key-2"), Value: getPtr("value-3")},
+			},
+		}
+		ctx, cancel := context.WithTimeout(context.Background(), shortTimeout)
+		_, err := s3client.PutBucketTagging(ctx, &s3.PutBucketTaggingInput{
+			Bucket:  &bucket,
+			Tagging: &tagging,
+		})
+		cancel()
+		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrDuplicateTagKey)); err != nil {
 			return err
 		}
 
@@ -2813,7 +2838,7 @@ func PutObject_invalid_long_tags(s *S3Conf) error {
 			Tagging: &tagging,
 		})
 		cancel()
-		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTag)); err != nil {
+		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTagValue)); err != nil {
 			return err
 		}
 
@@ -2827,7 +2852,7 @@ func PutObject_invalid_long_tags(s *S3Conf) error {
 		})
 		cancel()
 
-		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTag)); err != nil {
+		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTagValue)); err != nil {
 			return err
 		}
 
@@ -6991,7 +7016,7 @@ func PutObjectTagging_long_tags(s *S3Conf) error {
 			Key:     &obj,
 			Tagging: &tagging})
 		cancel()
-		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTag)); err != nil {
+		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTagKey)); err != nil {
 			return err
 		}
 
@@ -7003,7 +7028,39 @@ func PutObjectTagging_long_tags(s *S3Conf) error {
 			Key:     &obj,
 			Tagging: &tagging})
 		cancel()
-		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTag)); err != nil {
+		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTagValue)); err != nil {
+			return err
+		}
+
+		return nil
+	})
+}
+
+func PutObjectTagging_duplicate_keys(s *S3Conf) error {
+	testName := "PutObjectTagging_duplicate_keys"
+	return actionHandler(s, testName, func(s3client *s3.Client, bucket string) error {
+		obj := "my-obj"
+		_, err := putObjects(s3client, []string{obj}, bucket)
+		if err != nil {
+			return err
+		}
+
+		tagging := types.Tagging{
+			TagSet: []types.Tag{
+				{Key: getPtr("key-1"), Value: getPtr("value-1")},
+				{Key: getPtr("key-2"), Value: getPtr("value-2")},
+				{Key: getPtr("same-key"), Value: getPtr("value-3")},
+				{Key: getPtr("same-key"), Value: getPtr("value-4")},
+			},
+		}
+		ctx, cancel := context.WithTimeout(context.Background(), shortTimeout)
+		_, err = s3client.PutObjectTagging(ctx, &s3.PutObjectTaggingInput{
+			Bucket:  &bucket,
+			Key:     &obj,
+			Tagging: &tagging,
+		})
+		cancel()
+		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrDuplicateTagKey)); err != nil {
 			return err
 		}
 
@@ -7630,7 +7687,7 @@ func CreateMultipartUpload_with_invalid_tagging(s *S3Conf) error {
 			Tagging: getPtr("invalid_tag"),
 		})
 		cancel()
-		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTag)); err != nil {
+		if err := checkApiErr(err, s3err.GetAPIError(s3err.ErrInvalidTagValue)); err != nil {
 			return err
 		}