diff --git a/vertexai/_genai/_agent_engines_utils.py b/vertexai/_genai/_agent_engines_utils.py
index 1b9fc8ca79..405f9138b1 100644
--- a/vertexai/_genai/_agent_engines_utils.py
+++ b/vertexai/_genai/_agent_engines_utils.py
@@ -152,6 +152,8 @@
         "ag2",
         "llama-index",
         "custom",
+        "a2a",
+        "a2a-google-adk"
     ]
 )
 _DEFAULT_ASYNC_METHOD_NAME = "async_query"
diff --git a/vertexai/preview/reasoning_engines/templates/a2a.py b/vertexai/preview/reasoning_engines/templates/a2a.py
index 724e2af41e..a96533997c 100644
--- a/vertexai/preview/reasoning_engines/templates/a2a.py
+++ b/vertexai/preview/reasoning_engines/templates/a2a.py
@@ -212,6 +212,28 @@ def __init__(
         self.rest_handler = None
         self.task_store = None
         self.agent_executor = None
+        self._set_agent_framework()
+
+    def _set_agent_framework(self):
+        """Best effort detection of the underlying agent framework."""
+        self.agent_framework = "a2a"
+        agent_executor_builder = self._tmpl_attrs.get("agent_executor_builder")
+        if agent_executor_builder:
+            try:
+                from google.adk.a2a.executor.a2a_agent_executor import (
+                    A2aAgentExecutor as AdkAgentExecutor,
+                )
+                # It's unlikely that the builder does any heavy lifting, so this
+                # shouldn't throw any exception.
+                executor = agent_executor_builder(
+                    **self._tmpl_attrs.get("agent_executor_kwargs")
+                )
+                if isinstance(executor, AdkAgentExecutor):  # type: ignore
+                    # A2aAgentExecutor presence indicates a Google ADK agent
+                    # since it requires a `google.adk.runners.Runner` to instantiate.
+                    self.agent_framework = "a2a-google-adk"
+            except Exception:
+                pass
 
     def clone(self) -> "A2aAgent":
         """Clones the A2A agent."""