diff --git a/src/griffe_pydantic/_internal/extension.py b/src/griffe_pydantic/_internal/extension.py
index 8f14241..0b5594f 100644
--- a/src/griffe_pydantic/_internal/extension.py
+++ b/src/griffe_pydantic/_internal/extension.py
@@ -22,14 +22,21 @@
 class PydanticExtension(Extension):
     """Griffe extension for Pydantic."""
 
-    def __init__(self, *, schema: bool = False) -> None:
+    def __init__(
+        self,
+        *,
+        schema: bool = False,
+        extra_bases: list[str] | None = None,
+    ) -> None:
         """Initialize the extension.
 
         Parameters:
             schema: Whether to compute and store the JSON schema of models.
+            extra_bases: Additional base classes to detect as Pydantic models.
         """
         super().__init__()
         self._schema = schema
+        self._extra_bases = extra_bases or []
         self._processed: set[str] = set()
         self._recorded: list[tuple[ObjectNode, Class]] = []
 
@@ -37,10 +44,27 @@ def on_package(self, *, pkg: Module, **kwargs: Any) -> None:  # noqa: ARG002
         """Detect models once the whole package is loaded."""
         for node, cls in self._recorded:
             self._processed.add(cls.canonical_path)
-            dynamic._process_class(node.obj, cls, processed=self._processed, schema=self._schema)
-        static._process_module(pkg, processed=self._processed, schema=self._schema)
+            dynamic._process_class(
+                node.obj,
+                cls,
+                processed=self._processed,
+                schema=self._schema,
+            )
+        self._recorded.clear()
+        static._process_module(
+            pkg,
+            processed=self._processed,
+            schema=self._schema,
+            extra_bases=self._extra_bases,
+        )
 
-    def on_class_instance(self, *, node: ast.AST | ObjectNode, cls: Class, **kwargs: Any) -> None:  # noqa: ARG002
+    def on_class_instance(
+        self,
+        *,
+        node: ast.AST | ObjectNode,
+        cls: Class,
+        **kwargs: Any,  # noqa: ARG002
+    ) -> None:
         """Detect and prepare Pydantic models."""
         # Prevent running during static analysis.
         if isinstance(node, ast.AST):
@@ -52,5 +76,46 @@ def on_class_instance(self, *, node: ast.AST | ObjectNode, cls: Class, **kwargs:
             _logger.warning("could not import pydantic - models will not be detected")
             return
 
+        # Check if it's a standard Pydantic model
         if issubclass(node.obj, pydantic.BaseModel):
             self._recorded.append((node, cls))
+            return
+
+        # Check if it's a subclass of any extra base classes
+        for extra_base in self._extra_bases:
+            try:
+                # Import the extra base class
+                parts = extra_base.split(".")
+                module_name = ".".join(parts[:-1])
+                class_name = parts[-1]
+
+                if module_name:
+                    import importlib  # noqa: PLC0415
+
+                    module = importlib.import_module(module_name)
+                    base_class = getattr(module, class_name)
+                else:
+                    # Handle case where only class name is provided (in current module)
+                    base_class = globals().get(class_name)
+                    if base_class is None:
+                        continue
+
+                if base_class and issubclass(node.obj, base_class):
+                    try:
+                        # Verify that this extra base ultimately inherits from BaseModel
+                        if issubclass(base_class, pydantic.BaseModel):
+                            self._recorded.append((node, cls))
+                            return
+                        _logger.debug(f"Extra base class {extra_base} does not inherit from pydantic.BaseModel")
+                    except TypeError:
+                        # issubclass() can raise TypeError if base_class is not a class
+                        _logger.debug(f"Extra base {extra_base} is not a valid class for issubclass check")
+                        continue
+            except (ImportError, AttributeError):
+                # Skip if we can't import or resolve the extra base
+                _logger.debug(f"Could not resolve extra base class: {extra_base}")
+                continue
+            except TypeError:
+                # issubclass() with node.obj failed
+                _logger.debug(f"Could not check inheritance from extra base class: {extra_base}")
+                continue
diff --git a/src/griffe_pydantic/_internal/static.py b/src/griffe_pydantic/_internal/static.py
index 73993a0..aec1ee8 100644
--- a/src/griffe_pydantic/_internal/static.py
+++ b/src/griffe_pydantic/_internal/static.py
@@ -29,22 +29,28 @@
 _logger = get_logger("griffe_pydantic")
 
 
-def _inherits_pydantic(cls: Class) -> bool:
+def _inherits_pydantic(cls: Class, extra_bases: list[str] | None = None) -> bool:
     """Tell whether a class inherits from a Pydantic model.
 
     Parameters:
         cls: A Griffe class.
+        extra_bases: Additional base classes to consider as Pydantic models.
 
     Returns:
         True/False.
     """
+    extra_bases = extra_bases or []
+
     for base in cls.bases:
         if isinstance(base, (ExprName, Expr)):
             base = base.canonical_path  # noqa: PLW2901
         if base in {"pydantic.BaseModel", "pydantic.main.BaseModel"}:
             return True
+        # Check if the base matches any of the extra bases
+        if base in extra_bases:
+            return True
 
-    return any(_inherits_pydantic(parent_class) for parent_class in cls.mro())
+    return any(_inherits_pydantic(parent_class, extra_bases) for parent_class in cls.mro())
 
 
 def _pydantic_validator(func: Function) -> ExprCall | None:
@@ -123,7 +129,9 @@ def _process_attribute(attr: Attribute, cls: Class, *, processed: set[str]) -> N
         try:
             attr.docstring = Docstring(ast.literal_eval(docstring), parent=attr)  # type: ignore[arg-type]
         except ValueError:
-            _logger.debug(f"Could not parse description of field '{attr.path}' as literal, skipping")
+            _logger.debug(
+                f"Could not parse description of field '{attr.path}' as literal, skipping",
+            )
 
 
 def _process_function(func: Function, cls: Class, *, processed: set[str]) -> None:
@@ -141,12 +149,18 @@ def _process_function(func: Function, cls: Class, *, processed: set[str]) -> Non
         common._process_function(func, cls, fields)
 
 
-def _process_class(cls: Class, *, processed: set[str], schema: bool = False) -> None:
+def _process_class(
+    cls: Class,
+    *,
+    processed: set[str],
+    schema: bool = False,
+    extra_bases: list[str] | None = None,
+) -> None:
     """Finalize the Pydantic model data."""
     if cls.canonical_path in processed:
         return
 
-    if not _inherits_pydantic(cls):
+    if not _inherits_pydantic(cls, extra_bases):
         return
 
     processed.add(cls.canonical_path)
@@ -174,7 +188,12 @@ def _process_class(cls: Class, *, processed: set[str], schema: bool = False) ->
         elif kind is Kind.FUNCTION:
             _process_function(member, cls, processed=processed)  # type: ignore[arg-type]
         elif kind is Kind.CLASS:
-            _process_class(member, processed=processed, schema=schema)  # type: ignore[arg-type]
+            _process_class(
+                member,  # type: ignore[arg-type]
+                processed=processed,
+                schema=schema,
+                extra_bases=extra_bases,
+            )
 
 
 def _process_module(
@@ -182,6 +201,7 @@ def _process_module(
     *,
     processed: set[str],
     schema: bool = False,
+    extra_bases: list[str] | None = None,
 ) -> None:
     """Handle Pydantic models in a module."""
     if mod.canonical_path in processed:
@@ -191,7 +211,17 @@ def _process_module(
     for cls in mod.classes.values():
         # Don't process aliases, real classes will be processed at some point anyway.
         if not cls.is_alias:
-            _process_class(cls, processed=processed, schema=schema)
+            _process_class(
+                cls,
+                processed=processed,
+                schema=schema,
+                extra_bases=extra_bases,
+            )
 
     for submodule in mod.modules.values():
-        _process_module(submodule, processed=processed, schema=schema)
+        _process_module(
+            submodule,
+            processed=processed,
+            schema=schema,
+            extra_bases=extra_bases,
+        )
diff --git a/tests/test_api.py b/tests/test_api.py
index e1ef1b8..e4d4be1 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -73,18 +73,31 @@ def _yield_public_objects(
 
 
 @pytest.fixture(name="modulelevel_internal_objects", scope="module")
-def _fixture_modulelevel_internal_objects(internal_api: griffe.Module) -> list[griffe.Object | griffe.Alias]:
+def _fixture_modulelevel_internal_objects(
+    internal_api: griffe.Module,
+) -> list[griffe.Object | griffe.Alias]:
     return list(_yield_public_objects(internal_api, modulelevel=True))
 
 
 @pytest.fixture(name="internal_objects", scope="module")
-def _fixture_internal_objects(internal_api: griffe.Module) -> list[griffe.Object | griffe.Alias]:
+def _fixture_internal_objects(
+    internal_api: griffe.Module,
+) -> list[griffe.Object | griffe.Alias]:
     return list(_yield_public_objects(internal_api, modulelevel=False, special=True))
 
 
 @pytest.fixture(name="public_objects", scope="module")
-def _fixture_public_objects(public_api: griffe.Module) -> list[griffe.Object | griffe.Alias]:
-    return list(_yield_public_objects(public_api, modulelevel=False, inherited=True, special=True))
+def _fixture_public_objects(
+    public_api: griffe.Module,
+) -> list[griffe.Object | griffe.Alias]:
+    return list(
+        _yield_public_objects(
+            public_api,
+            modulelevel=False,
+            inherited=True,
+            special=True,
+        ),
+    )
 
 
 @pytest.fixture(name="inventory", scope="module")
@@ -96,7 +109,9 @@ def _fixture_inventory() -> Inventory:
         return Inventory.parse_sphinx(file)
 
 
-def test_exposed_objects(modulelevel_internal_objects: list[griffe.Object | griffe.Alias]) -> None:
+def test_exposed_objects(
+    modulelevel_internal_objects: list[griffe.Object | griffe.Alias],
+) -> None:
     """All public objects in the internal API are exposed under `griffe_pydantic`."""
     not_exposed = [
         obj.path
@@ -106,7 +121,9 @@ def test_exposed_objects(modulelevel_internal_objects: list[griffe.Object | grif
     assert not not_exposed, "Objects not exposed:\n" + "\n".join(sorted(not_exposed))
 
 
-def test_unique_names(modulelevel_internal_objects: list[griffe.Object | griffe.Alias]) -> None:
+def test_unique_names(
+    modulelevel_internal_objects: list[griffe.Object | griffe.Alias],
+) -> None:
     """All internal objects have unique names."""
     names_to_paths = defaultdict(list)
     for obj in modulelevel_internal_objects:
@@ -133,7 +150,10 @@ def _public_path(obj: griffe.Object | griffe.Alias) -> bool:
     )
 
 
-def test_api_matches_inventory(inventory: Inventory, public_objects: list[griffe.Object | griffe.Alias]) -> None:
+def test_api_matches_inventory(
+    inventory: Inventory,
+    public_objects: list[griffe.Object | griffe.Alias],
+) -> None:
     """All public objects are added to the inventory."""
     ignore_names = {"__getattr__", "__init__", "__repr__", "__str__", "__post_init__"}
     not_in_inventory = [
diff --git a/tests/test_extension.py b/tests/test_extension.py
index c540748..c86e87e 100644
--- a/tests/test_extension.py
+++ b/tests/test_extension.py
@@ -216,6 +216,30 @@ class Model(Base):
         assert "pydantic-field" not in package["Model.a"].labels
 
 
+def test_extra_bases() -> None:
+    """Test extra_bases functionality with custom base classes."""
+    code = """
+    from pydantic import BaseModel, Field
+
+    class CustomBase(BaseModel):
+        '''A custom base model.'''
+        pass
+
+    class CustomModel(CustomBase):
+        '''A model inheriting from custom base.'''
+        field1: str = Field(..., description="Test field")
+    """
+    with temporary_visited_package(
+        "package",
+        modules={"__init__.py": code},
+        extensions=Extensions(PydanticExtension(schema=False, extra_bases=["package.CustomBase"])),
+    ) as package:
+        # Both CustomBase and CustomModel should be detected
+        assert "pydantic-model" in package["CustomBase"].labels
+        assert "pydantic-model" in package["CustomModel"].labels
+        assert "pydantic-field" in package["CustomModel.field1"].labels
+
+
 def test_process_non_model_base_class_fields() -> None:
     """Fields in a non-model base class must be processed."""
     code = """