diff --git a/mem0/vector_stores/chroma.py b/mem0/vector_stores/chroma.py
index 0d399aad7..12f43cb4b 100644
--- a/mem0/vector_stores/chroma.py
+++ b/mem0/vector_stores/chroma.py
@@ -185,7 +185,11 @@ class ChromaDB(VectorStoreBase):
             vector (Optional[List[float]], optional): Updated vector. Defaults to None.
             payload (Optional[Dict], optional): Updated payload. Defaults to None.
         """
-        self.collection.update(ids=vector_id, embeddings=vector, metadatas=payload)
+        self.collection.update(
+            ids=[vector_id],
+            embeddings=[vector] if vector is not None else None,
+            metadatas=[payload] if payload is not None else None,
+        )
 
     def get(self, vector_id: str) -> Optional[OutputData]:
         """
diff --git a/tests/vector_stores/test_chroma.py b/tests/vector_stores/test_chroma.py
index bdea18602..dead40ba4 100644
--- a/tests/vector_stores/test_chroma.py
+++ b/tests/vector_stores/test_chroma.py
@@ -133,7 +133,31 @@ def test_update_vector(chromadb_instance):
     chromadb_instance.update(vector_id=vector_id, vector=new_vector, payload=new_payload)
 
     chromadb_instance.collection.update.assert_called_once_with(
-        ids=vector_id, embeddings=new_vector, metadatas=new_payload
+        ids=[vector_id], embeddings=[new_vector], metadatas=[new_payload]
+    )
+
+
+def test_update_vector_metadata_only(chromadb_instance):
+    # Metadata-only update (vector=None) must not wrap None in a list.
+    vector_id = "id1"
+    new_payload = {"name": "updated_vector"}
+
+    chromadb_instance.update(vector_id=vector_id, vector=None, payload=new_payload)
+
+    chromadb_instance.collection.update.assert_called_once_with(
+        ids=[vector_id], embeddings=None, metadatas=[new_payload]
+    )
+
+
+def test_update_vector_embedding_only(chromadb_instance):
+    # Vector-only update (payload=None) must not wrap None in a list.
+    vector_id = "id1"
+    new_vector = [0.7, 0.8, 0.9]
+
+    chromadb_instance.update(vector_id=vector_id, vector=new_vector, payload=None)
+
+    chromadb_instance.collection.update.assert_called_once_with(
+        ids=[vector_id], embeddings=[new_vector], metadatas=None
     )