diff --git a/server/src/internalClusterTest/java/org/opensearch/indices/settings/SearchOnlyReplicaIT.java b/server/src/internalClusterTest/java/org/opensearch/indices/settings/SearchOnlyReplicaIT.java
index 6bd91df1de66f..fa836e2cc5784 100644
--- a/server/src/internalClusterTest/java/org/opensearch/indices/settings/SearchOnlyReplicaIT.java
+++ b/server/src/internalClusterTest/java/org/opensearch/indices/settings/SearchOnlyReplicaIT.java
@@ -126,6 +126,8 @@ public void testFailoverWithSearchReplica_WithoutWriterReplicas() throws IOExcep
                 .put(indexSettings())
                 .put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, numWriterReplicas)
                 .put(IndexMetadata.SETTING_NUMBER_OF_SEARCH_REPLICAS, numSearchReplicas)
+                .put("index.refresh_interval", "40ms") // set lower interval so replica attempts replication cycles after primary is
+                                                       // removed.
                 .build()
         );
         ensureYellow(TEST_INDEX);
diff --git a/server/src/main/java/org/opensearch/indices/replication/PrimaryShardReplicationSource.java b/server/src/main/java/org/opensearch/indices/replication/PrimaryShardReplicationSource.java
index a17779810239a..af37594f88fee 100644
--- a/server/src/main/java/org/opensearch/indices/replication/PrimaryShardReplicationSource.java
+++ b/server/src/main/java/org/opensearch/indices/replication/PrimaryShardReplicationSource.java
@@ -47,6 +47,8 @@ public PrimaryShardReplicationSource(
         RecoverySettings recoverySettings,
         DiscoveryNode sourceNode
     ) {
+        assert targetNode != null : "Target node must be set";
+        assert sourceNode != null : "Source node must be set";
         this.targetAllocationId = targetAllocationId;
         this.transportService = transportService;
         this.sourceNode = sourceNode;
diff --git a/server/src/main/java/org/opensearch/indices/replication/SegmentReplicationSourceFactory.java b/server/src/main/java/org/opensearch/indices/replication/SegmentReplicationSourceFactory.java
index 81eb38757aebe..2b6723512abf2 100644
--- a/server/src/main/java/org/opensearch/indices/replication/SegmentReplicationSourceFactory.java
+++ b/server/src/main/java/org/opensearch/indices/replication/SegmentReplicationSourceFactory.java
@@ -53,6 +53,10 @@ public SegmentReplicationSource get(IndexShard shard) {
 
     private DiscoveryNode getPrimaryNode(ShardId shardId) {
         ShardRouting primaryShard = clusterService.state().routingTable().shardRoutingTable(shardId).primaryShard();
-        return clusterService.state().nodes().get(primaryShard.currentNodeId());
+        DiscoveryNode node = clusterService.state().nodes().get(primaryShard.currentNodeId());
+        if (node == null) {
+            throw new IllegalStateException("Cannot replicate, primary shard for " + shardId + " is not allocated on any node");
+        }
+        return node;
     }
 }
diff --git a/server/src/test/java/org/opensearch/indices/replication/SegmentReplicatorTests.java b/server/src/test/java/org/opensearch/indices/replication/SegmentReplicatorTests.java
index 7acee449a1b46..81ea16c80dd79 100644
--- a/server/src/test/java/org/opensearch/indices/replication/SegmentReplicatorTests.java
+++ b/server/src/test/java/org/opensearch/indices/replication/SegmentReplicatorTests.java
@@ -10,7 +10,13 @@
 
 import org.apache.lucene.store.IOContext;
 import org.opensearch.OpenSearchCorruptionException;
+import org.opensearch.cluster.ClusterState;
 import org.opensearch.cluster.metadata.IndexMetadata;
+import org.opensearch.cluster.routing.IndexRoutingTable;
+import org.opensearch.cluster.routing.IndexShardRoutingTable;
+import org.opensearch.cluster.routing.RoutingTable;
+import org.opensearch.cluster.routing.UnassignedInfo;
+import org.opensearch.cluster.service.ClusterService;
 import org.opensearch.common.lucene.Lucene;
 import org.opensearch.common.settings.Settings;
 import org.opensearch.core.action.ActionListener;
@@ -19,10 +25,12 @@
 import org.opensearch.index.shard.IndexShard;
 import org.opensearch.index.shard.IndexShardTestCase;
 import org.opensearch.index.store.StoreFileMetadata;
+import org.opensearch.indices.recovery.RecoverySettings;
 import org.opensearch.indices.replication.checkpoint.ReplicationCheckpoint;
 import org.opensearch.indices.replication.common.CopyState;
 import org.opensearch.indices.replication.common.ReplicationType;
 import org.opensearch.threadpool.ThreadPool;
+import org.opensearch.transport.TransportService;
 
 import java.io.IOException;
 import java.io.UncheckedIOException;
@@ -45,6 +53,48 @@ public class SegmentReplicatorTests extends IndexShardTestCase {
         .put(IndexMetadata.SETTING_REPLICATION_TYPE, ReplicationType.SEGMENT)
         .build();
 
+    public void testReplicationWithUnassignedPrimary() throws Exception {
+        final IndexShard replica = newStartedShard(false, settings, new NRTReplicationEngineFactory());
+        final IndexShard primary = newStartedShard(true, settings, new NRTReplicationEngineFactory());
+        SegmentReplicator replicator = new SegmentReplicator(threadPool);
+
+        ClusterService cs = mock(ClusterService.class);
+        IndexShardRoutingTable.Builder shardRoutingTable = new IndexShardRoutingTable.Builder(replica.shardId());
+        shardRoutingTable.addShard(replica.routingEntry());
+        shardRoutingTable.addShard(primary.routingEntry().moveToUnassigned(new UnassignedInfo(UnassignedInfo.Reason.NODE_LEFT, "test")));
+
+        when(cs.state()).thenReturn(buildClusterState(replica, shardRoutingTable));
+        replicator.setSourceFactory(new SegmentReplicationSourceFactory(mock(TransportService.class), mock(RecoverySettings.class), cs));
+        expectThrows(IllegalStateException.class, () -> replicator.startReplication(replica));
+        closeShards(replica, primary);
+    }
+
+    public void testReplicationWithUnknownPrimaryNode() throws Exception {
+        final IndexShard replica = newStartedShard(false, settings, new NRTReplicationEngineFactory());
+        final IndexShard primary = newStartedShard(true, settings, new NRTReplicationEngineFactory());
+        SegmentReplicator replicator = new SegmentReplicator(threadPool);
+
+        ClusterService cs = mock(ClusterService.class);
+        IndexShardRoutingTable.Builder shardRoutingTable = new IndexShardRoutingTable.Builder(replica.shardId());
+        shardRoutingTable.addShard(replica.routingEntry());
+        shardRoutingTable.addShard(primary.routingEntry());
+
+        when(cs.state()).thenReturn(buildClusterState(replica, shardRoutingTable));
+        replicator.setSourceFactory(new SegmentReplicationSourceFactory(mock(TransportService.class), mock(RecoverySettings.class), cs));
+        expectThrows(IllegalStateException.class, () -> replicator.startReplication(replica));
+        closeShards(replica, primary);
+    }
+
+    private ClusterState buildClusterState(IndexShard replica, IndexShardRoutingTable.Builder indexShard) {
+        return ClusterState.builder(clusterService.state())
+            .routingTable(
+                RoutingTable.builder()
+                    .add(IndexRoutingTable.builder(replica.shardId().getIndex()).addIndexShard(indexShard.build()).build())
+                    .build()
+            )
+            .build();
+    }
+
     public void testStartReplicationWithoutSourceFactory() {
         ThreadPool threadpool = mock(ThreadPool.class);
         ExecutorService mock = mock(ExecutorService.class);