diff --git a/server/src/main/java/org/opensearch/cluster/metadata/MetadataCreateIndexService.java b/server/src/main/java/org/opensearch/cluster/metadata/MetadataCreateIndexService.java
index 7973745ce84b3..50d25b11ef810 100644
--- a/server/src/main/java/org/opensearch/cluster/metadata/MetadataCreateIndexService.java
+++ b/server/src/main/java/org/opensearch/cluster/metadata/MetadataCreateIndexService.java
@@ -946,7 +946,8 @@ static Settings aggregateIndexSettings(
         if (INDEX_NUMBER_OF_SHARDS_SETTING.exists(indexSettingsBuilder) == false) {
             indexSettingsBuilder.put(SETTING_NUMBER_OF_SHARDS, INDEX_NUMBER_OF_SHARDS_SETTING.get(settings));
         }
-        if (INDEX_NUMBER_OF_REPLICAS_SETTING.exists(indexSettingsBuilder) == false) {
+        if (INDEX_NUMBER_OF_REPLICAS_SETTING.exists(indexSettingsBuilder) == false
+            || indexSettingsBuilder.get(SETTING_NUMBER_OF_REPLICAS) == null) {
             indexSettingsBuilder.put(SETTING_NUMBER_OF_REPLICAS, DEFAULT_REPLICA_COUNT_SETTING.get(currentState.metadata().settings()));
         }
         if (settings.get(SETTING_AUTO_EXPAND_REPLICAS) != null && indexSettingsBuilder.get(SETTING_AUTO_EXPAND_REPLICAS) == null) {
diff --git a/server/src/test/java/org/opensearch/cluster/metadata/MetadataCreateIndexServiceTests.java b/server/src/test/java/org/opensearch/cluster/metadata/MetadataCreateIndexServiceTests.java
index 0d86cfcca389c..86ca8b3ad6319 100644
--- a/server/src/test/java/org/opensearch/cluster/metadata/MetadataCreateIndexServiceTests.java
+++ b/server/src/test/java/org/opensearch/cluster/metadata/MetadataCreateIndexServiceTests.java
@@ -2151,6 +2151,33 @@ public void testAsyncDurabilityThrowsExceptionWhenRestrictSettingTrue() {
         );
     }
 
+    public void testAggregateIndexSettingsIndexReplicaIsSetToNull() {
+        // This checks that aggregateIndexSettings works for the case when the index setting `index.number_of_replicas` is set to null
+        request = new CreateIndexClusterStateUpdateRequest("create index", "test", "test");
+        request.settings(Settings.builder().putNull(SETTING_NUMBER_OF_REPLICAS).build());
+        Integer clusterDefaultReplicaNumber = 5;
+        Metadata metadata = new Metadata.Builder().persistentSettings(
+            Settings.builder().put("cluster.default_number_of_replicas", clusterDefaultReplicaNumber).build()
+        ).build();
+        ClusterState clusterState = ClusterState.builder(org.opensearch.cluster.ClusterName.CLUSTER_NAME_SETTING.getDefault(Settings.EMPTY))
+            .metadata(metadata)
+            .build();
+        Settings settings = Settings.builder().put(CLUSTER_REMOTE_INDEX_RESTRICT_ASYNC_DURABILITY_SETTING.getKey(), true).build();
+        clusterSettings = new ClusterSettings(settings, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS);
+        Settings aggregatedSettings = aggregateIndexSettings(
+            clusterState,
+            request,
+            Settings.EMPTY,
+            null,
+            Settings.EMPTY,
+            IndexScopedSettings.DEFAULT_SCOPED_SETTINGS,
+            randomShardLimitService(),
+            Collections.emptySet(),
+            clusterSettings
+        );
+        assertEquals(clusterDefaultReplicaNumber.toString(), aggregatedSettings.get(SETTING_NUMBER_OF_REPLICAS));
+    }
+
     public void testRequestDurabilityWhenRestrictSettingTrue() {
         // This checks that aggregateIndexSettings works for the case when the cluster setting
         // cluster.remote_store.index.restrict.async-durability is false or not set, it allows all types of durability modes