diff --git a/core-api/src/main/java/com/optimizely/ab/odp/ODPEventManager.java b/core-api/src/main/java/com/optimizely/ab/odp/ODPEventManager.java
index ce218ed9d..8edb135aa 100644
--- a/core-api/src/main/java/com/optimizely/ab/odp/ODPEventManager.java
+++ b/core-api/src/main/java/com/optimizely/ab/odp/ODPEventManager.java
@@ -108,10 +108,10 @@ public void identifyUser(@Nullable String vuid, @Nullable String userId) {
             identifiers.put(ODPUserKey.VUID.getKeyString(), vuid);
         }
         if (userId != null) {
-            if (isVuid(userId)) {
-                        identifiers.put(ODPUserKey.VUID.getKeyString(), userId);
+            if (ODPManager.isVuid(userId)) {
+                identifiers.put(ODPUserKey.VUID.getKeyString(), userId);
             } else {
-                        identifiers.put(ODPUserKey.FS_USER_ID.getKeyString(), userId);
+                identifiers.put(ODPUserKey.FS_USER_ID.getKeyString(), userId);
             }
         }
         ODPEvent event = new ODPEvent("fullstack", "identified", identifiers, null);
@@ -153,10 +153,6 @@ protected Map<String, String> augmentCommonIdentifiers(Map<String, String> sourc
         return identifiers;
     }
 
-    private boolean isVuid(String userId) {
-        return userId.startsWith("vuid_");
-    }
-
     private void processEvent(ODPEvent event) {
         if (!isRunning) {
             logger.warn("Failed to Process ODP Event. ODPEventManager is not running");
diff --git a/core-api/src/main/java/com/optimizely/ab/odp/ODPManager.java b/core-api/src/main/java/com/optimizely/ab/odp/ODPManager.java
index cacbcad0d..4f1ddc52d 100644
--- a/core-api/src/main/java/com/optimizely/ab/odp/ODPManager.java
+++ b/core-api/src/main/java/com/optimizely/ab/odp/ODPManager.java
@@ -68,6 +68,10 @@ public void close() {
         eventManager.stop();
     }
 
+    public static boolean isVuid(String userId) {
+        return userId.startsWith("vuid_");
+    }
+
     public static Builder builder() {
         return new Builder();
     }
diff --git a/core-api/src/main/java/com/optimizely/ab/odp/ODPSegmentManager.java b/core-api/src/main/java/com/optimizely/ab/odp/ODPSegmentManager.java
index 275c45ee1..ce1aaffd3 100644
--- a/core-api/src/main/java/com/optimizely/ab/odp/ODPSegmentManager.java
+++ b/core-api/src/main/java/com/optimizely/ab/odp/ODPSegmentManager.java
@@ -52,11 +52,15 @@ public ODPSegmentManager(ODPApiManager apiManager, Integer cacheSize, Integer ca
         this.segmentsCache = new DefaultLRUCache<>(cacheSize, cacheTimeoutSeconds);
     }
 
-    public List<String> getQualifiedSegments(String fsUserId) {
-        return getQualifiedSegments(ODPUserKey.FS_USER_ID, fsUserId, Collections.emptyList());
-    }
-    public List<String> getQualifiedSegments(String fsUserId, List<ODPSegmentOption> options) {
-        return getQualifiedSegments(ODPUserKey.FS_USER_ID, fsUserId, options);
+    public List<String> getQualifiedSegments(String userId) {
+        return getQualifiedSegments(userId, Collections.emptyList());
+    }
+    public List<String> getQualifiedSegments(String userId, List<ODPSegmentOption> options) {
+        if (ODPManager.isVuid(userId)) {
+            return getQualifiedSegments(ODPUserKey.VUID, userId, options);
+        } else {
+            return getQualifiedSegments(ODPUserKey.FS_USER_ID, userId, options);
+        }
     }
 
     public List<String> getQualifiedSegments(ODPUserKey userKey, String userValue) {
diff --git a/core-api/src/test/java/com/optimizely/ab/odp/ODPEventManagerTest.java b/core-api/src/test/java/com/optimizely/ab/odp/ODPEventManagerTest.java
index 27de838f3..0c1c01a2c 100644
--- a/core-api/src/test/java/com/optimizely/ab/odp/ODPEventManagerTest.java
+++ b/core-api/src/test/java/com/optimizely/ab/odp/ODPEventManagerTest.java
@@ -211,6 +211,64 @@ public void prepareCorrectPayloadForIdentifyUser() throws InterruptedException {
         }
     }
 
+    @Test
+    public void identifyUserWithVuidAndUserId() throws InterruptedException {
+        ODPEventManager eventManager = spy(new ODPEventManager(mockApiManager));
+        ArgumentCaptor<ODPEvent> captor = ArgumentCaptor.forClass(ODPEvent.class);
+
+        eventManager.identifyUser("vuid_123", "test-user");
+        verify(eventManager, times(1)).sendEvent(captor.capture());
+
+        ODPEvent event = captor.getValue();
+        Map<String, String> identifiers = event.getIdentifiers();
+        assertEquals(identifiers.size(), 2);
+        assertEquals(identifiers.get("vuid"), "vuid_123");
+        assertEquals(identifiers.get("fs_user_id"), "test-user");
+    }
+
+    @Test
+    public void identifyUserWithVuidOnly() throws InterruptedException {
+        ODPEventManager eventManager = spy(new ODPEventManager(mockApiManager));
+        ArgumentCaptor<ODPEvent> captor = ArgumentCaptor.forClass(ODPEvent.class);
+
+        eventManager.identifyUser("vuid_123", null);
+        verify(eventManager, times(1)).sendEvent(captor.capture());
+
+        ODPEvent event = captor.getValue();
+        Map<String, String> identifiers = event.getIdentifiers();
+        assertEquals(identifiers.size(), 1);
+        assertEquals(identifiers.get("vuid"), "vuid_123");
+    }
+
+    @Test
+    public void identifyUserWithUserIdOnly() throws InterruptedException {
+        ODPEventManager eventManager = spy(new ODPEventManager(mockApiManager));
+        ArgumentCaptor<ODPEvent> captor = ArgumentCaptor.forClass(ODPEvent.class);
+
+        eventManager.identifyUser(null, "test-user");
+        verify(eventManager, times(1)).sendEvent(captor.capture());
+
+        ODPEvent event = captor.getValue();
+        Map<String, String> identifiers = event.getIdentifiers();
+        assertEquals(identifiers.size(), 1);
+        assertEquals(identifiers.get("fs_user_id"), "test-user");
+    }
+
+    @Test
+    public void identifyUserWithVuidAsUserId() throws InterruptedException {
+        ODPEventManager eventManager = spy(new ODPEventManager(mockApiManager));
+        ArgumentCaptor<ODPEvent> captor = ArgumentCaptor.forClass(ODPEvent.class);
+
+        eventManager.identifyUser(null, "vuid_123");
+        verify(eventManager, times(1)).sendEvent(captor.capture());
+
+        ODPEvent event = captor.getValue();
+        Map<String, String> identifiers = event.getIdentifiers();
+        assertEquals(identifiers.size(), 1);
+        // SDK will convert userId to vuid when userId has a valid vuid format.
+        assertEquals(identifiers.get("vuid"), "vuid_123");
+    }
+
     @Test
     public void applyUpdatedODPConfigWhenAvailable() throws InterruptedException {
         Mockito.reset(mockApiManager);
diff --git a/core-api/src/test/java/com/optimizely/ab/odp/ODPManagerTest.java b/core-api/src/test/java/com/optimizely/ab/odp/ODPManagerTest.java
index 9673bfa69..1e1f59f29 100644
--- a/core-api/src/test/java/com/optimizely/ab/odp/ODPManagerTest.java
+++ b/core-api/src/test/java/com/optimizely/ab/odp/ODPManagerTest.java
@@ -121,4 +121,12 @@ public void shouldGetSegmentManager() {
         odpManager = ODPManager.builder().withApiManager(mockApiManager).build();
         assertNotNull(odpManager.getSegmentManager());
     }
+
+    @Test
+    public void isVuid() {
+        assertTrue(ODPManager.isVuid("vuid_123"));
+        assertFalse(ODPManager.isVuid("vuid123"));
+        assertFalse(ODPManager.isVuid("any_123"));
+        assertFalse(ODPManager.isVuid(""));
+    }
 }
diff --git a/core-api/src/test/java/com/optimizely/ab/odp/ODPSegmentManagerTest.java b/core-api/src/test/java/com/optimizely/ab/odp/ODPSegmentManagerTest.java
index 2e6aa611e..3d71f0d2c 100644
--- a/core-api/src/test/java/com/optimizely/ab/odp/ODPSegmentManagerTest.java
+++ b/core-api/src/test/java/com/optimizely/ab/odp/ODPSegmentManagerTest.java
@@ -398,4 +398,20 @@ public void noSegmentsInProjectAsync() throws InterruptedException {
 
         logbackVerifier.expectMessage(Level.DEBUG, "No Segments are used in the project, Not Fetching segments. Returning empty list");
     }
+
+    @Test
+    public void getQualifiedSegmentsWithUserId() {
+        ODPSegmentManager segmentManager = spy(new ODPSegmentManager(mockApiManager, mockCache));
+        segmentManager.getQualifiedSegments("test-user");
+        verify(segmentManager).getQualifiedSegments(ODPUserKey.FS_USER_ID, "test-user", Collections.emptyList());
+    }
+
+    @Test
+    public void getQualifiedSegmentsWithVuid() {
+        ODPSegmentManager segmentManager = spy(new ODPSegmentManager(mockApiManager, mockCache));
+        segmentManager.getQualifiedSegments("vuid_123");
+        // SDK will convert userId to vuid when userId has a valid vuid format.
+        verify(segmentManager).getQualifiedSegments(ODPUserKey.VUID, "vuid_123", Collections.emptyList());
+    }
+
 }