diff --git a/src/google/adk/a2a/utils/agent_card_builder.py b/src/google/adk/a2a/utils/agent_card_builder.py
index 047f786cc..9383ba83f 100644
--- a/src/google/adk/a2a/utils/agent_card_builder.py
+++ b/src/google/adk/a2a/utils/agent_card_builder.py
@@ -59,7 +59,7 @@ def __init__(
       agent: BaseAgent,
       rpc_url: Optional[str] = None,
       capabilities: Optional[AgentCapabilities] = None,
-      doc_url: Optional[str] = None,
+      documentation_url: Optional[str] = None,
       provider: Optional[AgentProvider] = None,
       agent_version: Optional[str] = None,
       security_schemes: Optional[Dict[str, SecurityScheme]] = None,
@@ -70,7 +70,7 @@ def __init__(
     self._agent = agent
     self._rpc_url = rpc_url or 'http://localhost:80/a2a'
     self._capabilities = capabilities or AgentCapabilities()
-    self._doc_url = doc_url
+    self._documentation_url = documentation_url or ""
     self._provider = provider
     self._security_schemes = security_schemes
     self._agent_version = agent_version or '0.0.1'
@@ -85,10 +85,10 @@ async def build(self) -> AgentCard:
       return AgentCard(
           name=self._agent.name,
           description=self._agent.description or 'An ADK Agent',
-          doc_url=self._doc_url,
           url=f"{self._rpc_url.rstrip('/')}",
           version=self._agent_version,
           capabilities=self._capabilities,
+          documentation_url=self._documentation_url,
           skills=all_skills,
           default_input_modes=['text/plain'],
           default_output_modes=['text/plain'],
diff --git a/tests/unittests/a2a/utils/test_agent_card_builder.py b/tests/unittests/a2a/utils/test_agent_card_builder.py
index 964c71889..f8d918f99 100644
--- a/tests/unittests/a2a/utils/test_agent_card_builder.py
+++ b/tests/unittests/a2a/utils/test_agent_card_builder.py
@@ -107,7 +107,7 @@ def test_init_with_valid_agent(self):
     assert builder._agent == mock_agent
     assert builder._rpc_url == "http://localhost:80/a2a"
     assert isinstance(builder._capabilities, AgentCapabilities)
-    assert builder._doc_url is None
+    assert builder._documentation_url == ""
     assert builder._provider is None
     assert builder._security_schemes is None
     assert builder._agent_version == "0.0.1"
@@ -126,7 +126,7 @@ def test_init_with_custom_parameters(self):
         agent=mock_agent,
         rpc_url="https://example.com/a2a",
         capabilities=mock_capabilities,
-        doc_url="https://docs.example.com",
+        documentation_url="https://docs.example.com",
         provider=mock_provider,
         agent_version="1.2.3",
         security_schemes=mock_security_schemes,
@@ -136,7 +136,7 @@ def test_init_with_custom_parameters(self):
     assert builder._agent == mock_agent
     assert builder._rpc_url == "https://example.com/a2a"
     assert builder._capabilities == mock_capabilities
-    assert builder._doc_url == "https://docs.example.com"
+    assert builder._documentation_url == "https://docs.example.com"
     assert builder._provider == mock_provider
     assert builder._security_schemes == mock_security_schemes
     assert builder._agent_version == "1.2.3"
@@ -181,7 +181,7 @@ async def test_build_success(
     assert isinstance(result, AgentCard)
     assert result.name == "test_agent"
     assert result.description == "Test agent description"
-    assert result.documentation_url is None
+    assert result.documentation_url == ""
     assert result.url == "http://localhost:80/a2a"
     assert result.version == "0.0.1"
     assert result.skills == [mock_primary_skill, mock_sub_skill]
@@ -213,8 +213,8 @@ async def test_build_with_custom_parameters(
     builder = AgentCardBuilder(
         agent=mock_agent,
         rpc_url="https://example.com/a2a/",
-        doc_url="https://docs.example.com",
         provider=mock_provider,
+        documentation_url="https://docs.example.com",
         agent_version="2.0.0",
         security_schemes=mock_security_schemes,
     )
@@ -227,10 +227,11 @@ async def test_build_with_custom_parameters(
     assert result.description == "An ADK Agent"  # Default description
     # The source code uses doc_url parameter but AgentCard expects documentation_url
     # Since the source code doesn't map doc_url to documentation_url, it will be None
-    assert result.documentation_url is None
+    assert result.documentation_url == "https://docs.example.com"
     assert (
         result.url == "https://example.com/a2a"
     )  # Should strip trailing slash
+    assert result.documentation_url == "https://docs.example.com"
     assert result.version == "2.0.0"
     assert result.provider == mock_provider
     assert result.security_schemes == mock_security_schemes