diff --git a/superset/mcp_service/chart/schemas.py b/superset/mcp_service/chart/schemas.py
index 28fdf1b0d88b..c5a2098442f9 100644
--- a/superset/mcp_service/chart/schemas.py
+++ b/superset/mcp_service/chart/schemas.py
@@ -45,6 +45,7 @@
 from superset.mcp_service.common.error_schemas import ChartGenerationError
 from superset.mcp_service.system.schemas import (
     PaginationInfo,
+    serialize_user_object,
     TagInfo,
     UserInfo,
 )
@@ -278,8 +279,9 @@ def serialize_chart_object(chart: ChartLike | None) -> ChartInfo | None:
         if getattr(chart, "tags", None)
         else [],
         owners=[
-            UserInfo.model_validate(owner, from_attributes=True)
+            info
             for owner in getattr(chart, "owners", [])
+            if (info := serialize_user_object(owner)) is not None
         ]
         if getattr(chart, "owners", None)
         else [],
diff --git a/superset/mcp_service/dashboard/schemas.py b/superset/mcp_service/dashboard/schemas.py
index 7b002677c698..e09b3871ce6c 100644
--- a/superset/mcp_service/dashboard/schemas.py
+++ b/superset/mcp_service/dashboard/schemas.py
@@ -87,6 +87,7 @@
 from superset.mcp_service.system.schemas import (
     PaginationInfo,
     RoleInfo,
+    serialize_user_object,
     TagInfo,
     UserInfo,
 )
@@ -109,19 +110,8 @@ def create(cls, error: str, error_type: str) -> "DashboardError":
         return cls(error=error, error_type=error_type, timestamp=datetime.now())
 
 
-def serialize_user_object(user: Any) -> UserInfo | None:
-    """Serialize a user object to UserInfo"""
-    if not user:
-        return None
-
-    return UserInfo(
-        id=getattr(user, "id", None),
-        username=getattr(user, "username", None),
-        first_name=getattr(user, "first_name", None),
-        last_name=getattr(user, "last_name", None),
-        email=getattr(user, "email", None),
-        active=getattr(user, "active", None),
-    )
+# serialize_user_object is imported from system.schemas and re-exported here
+# for backward compatibility with dashboard tool modules.
 
 
 def serialize_tag_object(tag: Any) -> TagInfo | None:
@@ -502,8 +492,9 @@ def dashboard_serializer(dashboard: "Dashboard") -> DashboardInfo:
         changed_on_humanized=dashboard.changed_on_humanized,
         chart_count=len(dashboard.slices) if dashboard.slices else 0,
         owners=[
-            UserInfo.model_validate(owner, from_attributes=True)
+            info
             for owner in dashboard.owners
+            if (info := serialize_user_object(owner)) is not None
         ]
         if dashboard.owners
         else [],
diff --git a/superset/mcp_service/dataset/schemas.py b/superset/mcp_service/dataset/schemas.py
index b0dad96b5926..14dd329e8f7d 100644
--- a/superset/mcp_service/dataset/schemas.py
+++ b/superset/mcp_service/dataset/schemas.py
@@ -37,6 +37,7 @@
 from superset.mcp_service.common.cache_schemas import MetadataCacheControl
 from superset.mcp_service.system.schemas import (
     PaginationInfo,
+    serialize_user_object,
     TagInfo,
     UserInfo,
 )
@@ -338,8 +339,9 @@ def serialize_dataset_object(dataset: Any) -> DatasetInfo | None:
         if getattr(dataset, "tags", None)
         else [],
         owners=[
-            UserInfo.model_validate(owner, from_attributes=True)
+            info
             for owner in getattr(dataset, "owners", [])
+            if (info := serialize_user_object(owner)) is not None
         ]
         if getattr(dataset, "owners", None)
         else [],
diff --git a/superset/mcp_service/system/schemas.py b/superset/mcp_service/system/schemas.py
index f1667471693f..9810cc4d3b3e 100644
--- a/superset/mcp_service/system/schemas.py
+++ b/superset/mcp_service/system/schemas.py
@@ -25,7 +25,7 @@
 from __future__ import annotations
 
 from datetime import datetime
-from typing import Dict, List
+from typing import Any, Dict, List
 
 from pydantic import BaseModel, ConfigDict, Field
 
@@ -170,6 +170,29 @@ class UserInfo(BaseModel):
     )
 
 
+def serialize_user_object(user: Any) -> UserInfo | None:
+    """Serialize a user ORM object to UserInfo, extracting role names as strings."""
+    if not user:
+        return None
+
+    user_roles: list[str] = []
+    if (raw_roles := getattr(user, "roles", None)) is not None:
+        try:
+            user_roles = [role.name for role in raw_roles if hasattr(role, "name")]
+        except TypeError:
+            user_roles = []
+
+    return UserInfo(
+        id=getattr(user, "id", None),
+        username=getattr(user, "username", None),
+        first_name=getattr(user, "first_name", None),
+        last_name=getattr(user, "last_name", None),
+        email=getattr(user, "email", None),
+        active=getattr(user, "active", None),
+        roles=user_roles,
+    )
+
+
 class TagInfo(BaseModel):
     id: int | None = None
     name: str | None = None
diff --git a/tests/unit_tests/mcp_service/system/test_serialize_user_object.py b/tests/unit_tests/mcp_service/system/test_serialize_user_object.py
new file mode 100644
index 000000000000..adca76fdfde9
--- /dev/null
+++ b/tests/unit_tests/mcp_service/system/test_serialize_user_object.py
@@ -0,0 +1,167 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+from unittest.mock import MagicMock
+
+import pytest
+
+from superset.mcp_service.system.schemas import serialize_user_object
+
+
+def test_returns_none_for_none_user() -> None:
+    assert serialize_user_object(None) is None
+
+
+def test_returns_none_for_falsy_user() -> None:
+    assert serialize_user_object(0) is None
+    assert serialize_user_object("") is None
+
+
+def test_extracts_basic_fields() -> None:
+    user = MagicMock()
+    user.id = 1
+    user.username = "admin"
+    user.first_name = "Ad"
+    user.last_name = "Min"
+    user.email = "admin@example.com"
+    user.active = True
+    user.roles = []
+
+    result = serialize_user_object(user)
+
+    assert result is not None
+    assert result.id == 1
+    assert result.username == "admin"
+    assert result.first_name == "Ad"
+    assert result.last_name == "Min"
+    assert result.email == "admin@example.com"
+    assert result.active is True
+    assert result.roles == []
+
+
+def test_extracts_role_names_from_orm_objects() -> None:
+    """The original bug: SQLAlchemy Role objects must be converted to strings."""
+    role_admin = MagicMock()
+    role_admin.name = "Admin"
+    role_alpha = MagicMock()
+    role_alpha.name = "Alpha"
+
+    user = MagicMock()
+    user.id = 1
+    user.username = "admin"
+    user.first_name = "Ad"
+    user.last_name = "Min"
+    user.email = "admin@example.com"
+    user.active = True
+    user.roles = [role_admin, role_alpha]
+
+    result = serialize_user_object(user)
+
+    assert result is not None
+    assert result.roles == ["Admin", "Alpha"]
+
+
+def test_handles_user_without_roles_attribute() -> None:
+    user = MagicMock(
+        spec=["id", "username", "first_name", "last_name", "email", "active"]
+    )
+    user.id = 1
+    user.username = "noroles"
+    user.first_name = "No"
+    user.last_name = "Roles"
+    user.email = "no@roles.com"
+    user.active = True
+
+    result = serialize_user_object(user)
+
+    assert result is not None
+    assert result.roles == []
+
+
+def _make_user(**overrides: object) -> MagicMock:
+    """Helper to create a fully-populated mock user."""
+    defaults = {
+        "id": 1,
+        "username": "testuser",
+        "first_name": "Test",
+        "last_name": "User",
+        "email": "test@example.com",
+        "active": True,
+        "roles": [],
+    }
+    defaults.update(overrides)
+    user = MagicMock()
+    for k, v in defaults.items():
+        setattr(user, k, v)
+    return user
+
+
+def test_handles_non_iterable_roles() -> None:
+    user = _make_user(roles=42)
+
+    result = serialize_user_object(user)
+
+    assert result is not None
+    assert result.roles == []
+
+
+def test_skips_roles_without_name_attribute() -> None:
+    role_good = MagicMock()
+    role_good.name = "Admin"
+
+    user = _make_user(roles=[role_good])
+
+    result = serialize_user_object(user)
+
+    assert result is not None
+    assert result.roles == ["Admin"]
+
+
+def test_handles_none_roles() -> None:
+    user = _make_user(roles=None)
+
+    result = serialize_user_object(user)
+
+    assert result is not None
+    assert result.roles == []
+
+
+@pytest.mark.parametrize(
+    "missing_field",
+    ["id", "username", "first_name", "last_name", "email", "active"],
+)
+def test_missing_fields_default_to_none(missing_field: str) -> None:
+    """Fields not present on the user object should default to None."""
+    attrs = {
+        "id": 1,
+        "username": "test",
+        "first_name": "T",
+        "last_name": "U",
+        "email": "t@e.com",
+        "active": True,
+        "roles": [],
+    }
+    # Remove the field under test
+    del attrs[missing_field]
+    user = MagicMock(spec=list(attrs.keys()))
+    for k, v in attrs.items():
+        setattr(user, k, v)
+
+    result = serialize_user_object(user)
+
+    assert result is not None
+    assert getattr(result, missing_field) is None