diff --git a/src/google/adk/cli/fast_api.py b/src/google/adk/cli/fast_api.py
index 7d93b54360..d1862ceba2 100644
--- a/src/google/adk/cli/fast_api.py
+++ b/src/google/adk/cli/fast_api.py
@@ -38,6 +38,7 @@
 from ..auth.credential_service.in_memory_credential_service import InMemoryCredentialService
 from ..evaluation.local_eval_set_results_manager import LocalEvalSetResultsManager
 from ..evaluation.local_eval_sets_manager import LocalEvalSetsManager
+from ..memory.base_memory_service import BaseMemoryService
 from ..memory.in_memory_memory_service import InMemoryMemoryService
 from ..memory.vertex_ai_memory_bank_service import VertexAiMemoryBankService
 from ..runners import Runner
@@ -60,6 +61,7 @@ def get_fast_api_app(
     session_db_kwargs: Optional[Mapping[str, Any]] = None,
     artifact_service_uri: Optional[str] = None,
     memory_service_uri: Optional[str] = None,
+    memory_service: Optional[BaseMemoryService] = None,
     eval_storage_uri: Optional[str] = None,
     allow_origins: Optional[list[str]] = None,
     web: bool,
@@ -107,31 +109,32 @@ def _parse_agent_engine_resource_name(agent_engine_id_or_resource_name):
     return project, location, agent_engine_id
 
   # Build the Memory service
-  if memory_service_uri:
-    if memory_service_uri.startswith("rag://"):
-      from ..memory.vertex_ai_rag_memory_service import VertexAiRagMemoryService
-
-      rag_corpus = memory_service_uri.split("://")[1]
-      if not rag_corpus:
-        raise click.ClickException("Rag corpus can not be empty.")
-      envs.load_dotenv_for_agent("", agents_dir)
-      memory_service = VertexAiRagMemoryService(
-          rag_corpus=f'projects/{os.environ["GOOGLE_CLOUD_PROJECT"]}/locations/{os.environ["GOOGLE_CLOUD_LOCATION"]}/ragCorpora/{rag_corpus}'
-      )
-    elif memory_service_uri.startswith("agentengine://"):
-      agent_engine_id_or_resource_name = memory_service_uri.split("://")[1]
-      project, location, agent_engine_id = _parse_agent_engine_resource_name(
-          agent_engine_id_or_resource_name
-      )
-      memory_service = VertexAiMemoryBankService(
-          project=project,
-          location=location,
-          agent_engine_id=agent_engine_id,
-      )
-    else:
-      raise click.ClickException(
-          "Unsupported memory service URI: %s" % memory_service_uri
-      )
+  if not memory_service:
+    if memory_service_uri:
+      if memory_service_uri.startswith("rag://"):
+        from ..memory.vertex_ai_rag_memory_service import VertexAiRagMemoryService
+
+        rag_corpus = memory_service_uri.split("://")[1]
+        if not rag_corpus:
+          raise click.ClickException("Rag corpus can not be empty.")
+        envs.load_dotenv_for_agent("", agents_dir)
+        memory_service = VertexAiRagMemoryService(
+            rag_corpus=f'projects/{os.environ["GOOGLE_CLOUD_PROJECT"]}/locations/{os.environ["GOOGLE_CLOUD_LOCATION"]}/ragCorpora/{rag_corpus}'
+        )
+      elif memory_service_uri.startswith("agentengine://"):
+        agent_engine_id_or_resource_name = memory_service_uri.split("://")[1]
+        project, location, agent_engine_id = _parse_agent_engine_resource_name(
+            agent_engine_id_or_resource_name
+        )
+        memory_service = VertexAiMemoryBankService(
+            project=project,
+            location=location,
+            agent_engine_id=agent_engine_id,
+        )
+      else:
+        raise click.ClickException(
+            "Unsupported memory service URI: %s" % memory_service_uri
+        )
   else:
     memory_service = InMemoryMemoryService()