diff --git a/server/src/main/java/org/opensearch/cluster/coordination/ClusterBootstrapService.java b/server/src/main/java/org/opensearch/cluster/coordination/ClusterBootstrapService.java
index 8df561149eb3d..c7708a54f9031 100644
--- a/server/src/main/java/org/opensearch/cluster/coordination/ClusterBootstrapService.java
+++ b/server/src/main/java/org/opensearch/cluster/coordination/ClusterBootstrapService.java
@@ -113,12 +113,12 @@ public ClusterBootstrapService(
         BooleanSupplier isBootstrappedSupplier,
         Consumer<VotingConfiguration> votingConfigurationConsumer
     ) {
+        // TODO: Remove variable 'initialClusterManagerSettingName' after removing MASTER_ROLE.
+        String initialClusterManagerSettingName = INITIAL_CLUSTER_MANAGER_NODES_SETTING.exists(settings)
+            ? INITIAL_CLUSTER_MANAGER_NODES_SETTING.getKey()
+            : INITIAL_MASTER_NODES_SETTING.getKey();
         if (DiscoveryModule.isSingleNodeDiscovery(settings)) {
             if (INITIAL_CLUSTER_MANAGER_NODES_SETTING.existsOrFallbackExists(settings)) {
-                // TODO: Remove variable 'initialClusterManagerSettingName' after removing MASTER_ROLE.
-                String initialClusterManagerSettingName = INITIAL_CLUSTER_MANAGER_NODES_SETTING.exists(settings)
-                    ? INITIAL_CLUSTER_MANAGER_NODES_SETTING.getKey()
-                    : INITIAL_MASTER_NODES_SETTING.getKey();
                 throw new IllegalArgumentException(
                     "setting ["
                         + initialClusterManagerSettingName
@@ -145,7 +145,7 @@ public ClusterBootstrapService(
             bootstrapRequirements = unmodifiableSet(new LinkedHashSet<>(initialMasterNodes));
             if (bootstrapRequirements.size() != initialMasterNodes.size()) {
                 throw new IllegalArgumentException(
-                    "setting [" + INITIAL_CLUSTER_MANAGER_NODES_SETTING.getKey() + "] contains duplicates: " + initialMasterNodes
+                    "setting [" + initialClusterManagerSettingName + "] contains duplicates: " + initialMasterNodes
                 );
             }
             unconfiguredBootstrapTimeout = discoveryIsConfigured(settings) ? null : UNCONFIGURED_BOOTSTRAP_TIMEOUT_SETTING.get(settings);
@@ -163,7 +163,8 @@ public static boolean discoveryIsConfigured(Settings settings) {
             LEGACY_DISCOVERY_HOSTS_PROVIDER_SETTING,
             DISCOVERY_SEED_HOSTS_SETTING,
             LEGACY_DISCOVERY_ZEN_PING_UNICAST_HOSTS_SETTING,
-            INITIAL_CLUSTER_MANAGER_NODES_SETTING
+            INITIAL_CLUSTER_MANAGER_NODES_SETTING,
+            INITIAL_MASTER_NODES_SETTING
         ).anyMatch(s -> s.exists(settings));
     }
 
diff --git a/server/src/test/java/org/opensearch/bootstrap/BootstrapChecksTests.java b/server/src/test/java/org/opensearch/bootstrap/BootstrapChecksTests.java
index d941c624509da..c59ca1dd60dc7 100644
--- a/server/src/test/java/org/opensearch/bootstrap/BootstrapChecksTests.java
+++ b/server/src/test/java/org/opensearch/bootstrap/BootstrapChecksTests.java
@@ -818,5 +818,7 @@ public void testDiscoveryConfiguredCheck() throws NodeValidationException {
         ensureChecksPass.accept(Settings.builder().putList(ClusterBootstrapService.INITIAL_CLUSTER_MANAGER_NODES_SETTING.getKey()));
         ensureChecksPass.accept(Settings.builder().putList(DiscoveryModule.DISCOVERY_SEED_PROVIDERS_SETTING.getKey()));
         ensureChecksPass.accept(Settings.builder().putList(SettingsBasedSeedHostsProvider.DISCOVERY_SEED_HOSTS_SETTING.getKey()));
+        // Validate the deprecated setting is still valid during the node bootstrap.
+        ensureChecksPass.accept(Settings.builder().putList(ClusterBootstrapService.INITIAL_MASTER_NODES_SETTING.getKey()));
     }
 }
diff --git a/server/src/test/java/org/opensearch/cluster/coordination/ClusterBootstrapServiceTests.java b/server/src/test/java/org/opensearch/cluster/coordination/ClusterBootstrapServiceTests.java
index dd55d078fe2c6..3e4148cef61cd 100644
--- a/server/src/test/java/org/opensearch/cluster/coordination/ClusterBootstrapServiceTests.java
+++ b/server/src/test/java/org/opensearch/cluster/coordination/ClusterBootstrapServiceTests.java
@@ -166,10 +166,19 @@ public void testDoesNothingByDefaultIfSeedHostsConfigured() {
         testDoesNothingWithSettings(builder().putList(DISCOVERY_SEED_HOSTS_SETTING.getKey()));
     }
 
-    public void testDoesNothingByDefaultIfMasterNodesConfigured() {
+    public void testDoesNothingByDefaultIfClusterManagerNodesConfigured() {
         testDoesNothingWithSettings(builder().putList(INITIAL_CLUSTER_MANAGER_NODES_SETTING.getKey()));
     }
 
+    // Validate the deprecated setting is still valid during the cluster bootstrap.
+    public void testDoesNothingByDefaultIfMasterNodesConfigured() {
+        testDoesNothingWithSettings(builder().putList(INITIAL_MASTER_NODES_SETTING.getKey()));
+        assertWarnings(
+            "[cluster.initial_master_nodes] setting was deprecated in OpenSearch and will be removed in a future release! "
+                + "See the breaking changes documentation for the next major version."
+        );
+    }
+
     public void testDoesNothingByDefaultOnMasterIneligibleNodes() {
         localNode = new DiscoveryNode(
             "local",