diff --git a/src/google/adk/sessions/database_session_service.py b/src/google/adk/sessions/database_session_service.py
index d033f1f234..740e5540d9 100644
--- a/src/google/adk/sessions/database_session_service.py
+++ b/src/google/adk/sessions/database_session_service.py
@@ -461,7 +461,8 @@ async def create_session(
       now = datetime.fromtimestamp(platform_time.get_time(), tz=timezone.utc)
       is_sqlite = self.db_engine.dialect.name == _SQLITE_DIALECT
       is_postgresql = self.db_engine.dialect.name == _POSTGRESQL_DIALECT
-      if is_sqlite or is_postgresql:
+      is_mysql = self.db_engine.dialect.name == _MYSQL_DIALECT
+      if is_sqlite or is_postgresql or is_mysql:
         now = now.replace(tzinfo=None)
 
       storage_session = schema.StorageSession(
diff --git a/tests/unittests/sessions/test_session_service.py b/tests/unittests/sessions/test_session_service.py
index 2d7d89f15f..6eda8d288c 100644
--- a/tests/unittests/sessions/test_session_service.py
+++ b/tests/unittests/sessions/test_session_service.py
@@ -102,44 +102,47 @@ def fake_create_async_engine(_db_url: str, **kwargs):
   assert captured_kwargs.get('pool_pre_ping') is True
 
 
-@pytest.mark.parametrize('dialect_name', ['sqlite', 'postgresql'])
+@pytest.mark.parametrize('dialect_name', ['sqlite', 'postgresql', 'mysql'])
 def test_database_session_service_strips_timezone_for_dialect(dialect_name):
   """Verifies that timezone-aware datetimes are converted to naive datetimes
-  for SQLite and PostgreSQL to avoid 'can't subtract offset-naive and
-  offset-aware datetimes' errors.
+  for SQLite, PostgreSQL, and MySQL.
 
   PostgreSQL's default TIMESTAMP type is WITHOUT TIME ZONE, which cannot
   accept timezone-aware datetime objects when using asyncpg. SQLite also
-  requires naive datetimes.
+  requires naive datetimes. MySQL's DATETIME type silently drops timezone
+  info, causing stale-writer false positives when the marker string differs
+  between tz-aware writes and naive reads.
   """
   # Simulate the logic in create_session
   is_sqlite = dialect_name == 'sqlite'
   is_postgres = dialect_name == 'postgresql'
+  is_mysql = dialect_name == 'mysql'
 
   now = datetime.now(timezone.utc)
   assert now.tzinfo is not None  # Starts with timezone
 
-  if is_sqlite or is_postgres:
+  if is_sqlite or is_postgres or is_mysql:
     now = now.replace(tzinfo=None)
 
-  # Both SQLite and PostgreSQL should have timezone stripped
+  # SQLite, PostgreSQL, and MySQL should have timezone stripped
   assert now.tzinfo is None
 
 
 def test_database_session_service_preserves_timezone_for_other_dialects():
   """Verifies that timezone info is preserved for dialects that support it."""
-  # For dialects like MySQL with explicit timezone support, we don't strip
-  dialect_name = 'mysql'
+  # For dialects like Spanner with explicit timezone support, we don't strip
+  dialect_name = 'spanner'
   is_sqlite = dialect_name == 'sqlite'
   is_postgres = dialect_name == 'postgresql'
+  is_mysql = dialect_name == 'mysql'
 
   now = datetime.now(timezone.utc)
   assert now.tzinfo is not None
 
-  if is_sqlite or is_postgres:
+  if is_sqlite or is_postgres or is_mysql:
     now = now.replace(tzinfo=None)
 
-  # MySQL should preserve timezone (if the column type supports it)
+  # Spanner should preserve timezone
   assert now.tzinfo is not None