diff --git a/alternator/executor.cc b/alternator/executor.cc
index f0c075424d..3afc5253d1 100644
--- a/alternator/executor.cc
+++ b/alternator/executor.cc
@@ -354,6 +354,20 @@ static schema_ptr get_table_from_batch_request(const service::storage_proxy& pro
     }
 }
 
+using primary_key = std::pair<partition_key, clustering_key>;
+struct primary_key_hash {
+    schema_ptr _s;
+    size_t operator()(const primary_key& key) const {
+        return utils::hash_combine(partition_key::hashing(*_s)(key.first), clustering_key::hashing(*_s)(key.second));
+    }
+};
+struct primary_key_equal {
+    schema_ptr _s;
+    bool operator()(const primary_key& k1, const primary_key& k2) const {
+        return partition_key::equality(*_s)(k1.first, k2.first) && clustering_key::equality(*_s)(k1.second, k2.second);
+    }
+};
+
 future<json::json_return_type> executor::batch_write_item(std::string content) {
     _stats.api_operations.batch_write_item++;
     Json::Value batch_info = json::to_json_value(content);
@@ -361,8 +375,10 @@ future<json::json_return_type> executor::batch_write_item(std::string content) {
 
     std::vector<mutation> mutations;
     mutations.reserve(request_items.size());
+
     for (auto it = request_items.begin(); it != request_items.end(); ++it) {
         schema_ptr schema = get_table_from_batch_request(_proxy, it);
+        std::unordered_set<primary_key, primary_key_hash, primary_key_equal> used_keys(1, primary_key_hash{schema}, primary_key_equal{schema});
         for (auto&& request : *it) {
             if (!request.isObject() || request.size() != 1) {
                 throw api_error("ValidationException", format("Invalid BatchWriteItem request: {}", request.toStyledString()));
@@ -372,9 +388,21 @@ future<json::json_return_type> executor::batch_write_item(std::string content) {
                 const Json::Value& put_request = *r;
                 const Json::Value& item = put_request["Item"];
                 mutations.push_back(make_item_mutation(item, schema));
+                // make_item_mutation returns a mutation with a single clustering row
+                auto mut_key = std::make_pair(mutations.back().key(), mutations.back().partition().clustered_rows().begin()->key());
+                if (used_keys.count(mut_key) > 0) {
+                    throw api_error("ValidationException", "Provided list of item keys contains duplicates");
+                }
+                used_keys.insert(std::move(mut_key));
             } else if (r.key() == "DeleteRequest") {
                 const Json::Value& key = (*r)["Key"];
                 mutations.push_back(make_delete_item_mutation(key, schema));
+                // make_delete_item_mutation returns a mutation with a single clustering row
+                auto mut_key = std::make_pair(mutations.back().key(), mutations.back().partition().clustered_rows().begin()->key());
+                if (used_keys.count(mut_key) > 0) {
+                    throw api_error("ValidationException", "Provided list of item keys contains duplicates");
+                }
+                used_keys.insert(std::move(mut_key));
             } else {
                 throw api_error("ValidationException", format("Unknown BatchWriteItem request type: {}", r.key()));
             }