diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index 5c1126fbc4d..c816efd083c 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -75,6 +75,8 @@ Bug fixes
   By `Kai Mühlbauer <https://github.com/kmuehlbauer>`_.
 - Fix weighted ``polyfit`` for arrays with more than two dimensions (:issue:`9972`, :pull:`9974`).
   By `Mattia Almansi <https://github.com/malmans2>`_.
+- Include accessors in ``__dir__`` (:pull:`9985`).
+  By `Justus Magin <https://github.com/keewis>`_.
 
 Documentation
 ~~~~~~~~~~~~~
diff --git a/xarray/core/common.py b/xarray/core/common.py
index 3a70c9ec585..51123c8f503 100644
--- a/xarray/core/common.py
+++ b/xarray/core/common.py
@@ -6,7 +6,7 @@
 from contextlib import suppress
 from html import escape
 from textwrap import dedent
-from typing import TYPE_CHECKING, Any, TypeVar, Union, overload
+from typing import TYPE_CHECKING, Any, ClassVar, TypeVar, Union, overload
 
 import numpy as np
 import pandas as pd
@@ -262,6 +262,16 @@ def sizes(self: Any) -> Mapping[Hashable, int]:
         return Frozen(dict(zip(self.dims, self.shape, strict=True)))
 
 
+class AccessorMixin:
+    """Mixin class that exposes accessors through __dir__"""
+
+    __slots__ = ()
+    _accessors: ClassVar[set[str]]
+
+    def __dir__(self):
+        return sorted(set(super().__dir__()) | type(self)._accessors)
+
+
 class AttrAccessMixin:
     """Mixin class that allows getting keys with attribute access"""
 
@@ -351,7 +361,7 @@ def __dir__(self) -> list[str]:
             for item in source
             if isinstance(item, str)
         }
-        return sorted(set(dir(type(self))) | extra_attrs)
+        return sorted(set(super().__dir__()) | extra_attrs)
 
     def _ipython_key_completions_(self) -> list[str]:
         """Provide method for the key-autocompletions in IPython.
diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index d287564cfe5..b18a2c59903 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -16,6 +16,7 @@
 from typing import (
     TYPE_CHECKING,
     Any,
+    ClassVar,
     Generic,
     Literal,
     NoReturn,
@@ -38,7 +39,12 @@
     align,
 )
 from xarray.core.arithmetic import DataArrayArithmetic
-from xarray.core.common import AbstractArray, DataWithCoords, get_chunksizes
+from xarray.core.common import (
+    AbstractArray,
+    AccessorMixin,
+    DataWithCoords,
+    get_chunksizes,
+)
 from xarray.core.computation import unify_chunks
 from xarray.core.coordinates import (
     Coordinates,
@@ -281,6 +287,7 @@ class DataArray(
     DataWithCoords,
     DataArrayArithmetic,
     DataArrayAggregations,
+    AccessorMixin,
 ):
     """N-dimensional array with labeled coordinates and dimensions.
 
@@ -421,6 +428,7 @@ class DataArray(
     _indexes: dict[Hashable, Index]
     _name: Hashable | None
     _variable: Variable
+    _accessors: ClassVar[set[str]] = set()
 
     __slots__ = (
         "__weakref__",
diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 74f90ce9eea..3c3691f74f2 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -24,7 +24,7 @@
 from operator import methodcaller
 from os import PathLike
 from types import EllipsisType
-from typing import IO, TYPE_CHECKING, Any, Generic, Literal, cast, overload
+from typing import IO, TYPE_CHECKING, Any, ClassVar, Generic, Literal, cast, overload
 
 import numpy as np
 from pandas.api.types import is_extension_array_dtype
@@ -57,6 +57,7 @@
 from xarray.core.arithmetic import DatasetArithmetic
 from xarray.core.array_api_compat import to_like_array
 from xarray.core.common import (
+    AccessorMixin,
     DataWithCoords,
     _contains_datetime_like_objects,
     get_chunksizes,
@@ -550,6 +551,7 @@ class Dataset(
     DataWithCoords,
     DatasetAggregations,
     DatasetArithmetic,
+    AccessorMixin,
     Mapping[Hashable, "DataArray"],
 ):
     """A multi-dimensional, in memory, array database.
@@ -709,6 +711,7 @@ class Dataset(
     _close: Callable[[], None] | None
     _indexes: dict[Hashable, Index]
     _variables: dict[Hashable, Variable]
+    _accessors: ClassVar[set[str]] = set()
 
     __slots__ = (
         "__weakref__",
diff --git a/xarray/core/datatree.py b/xarray/core/datatree.py
index ee90cf7477c..2465fe488ba 100644
--- a/xarray/core/datatree.py
+++ b/xarray/core/datatree.py
@@ -12,13 +12,13 @@
     Mapping,
 )
 from html import escape
-from typing import TYPE_CHECKING, Any, Literal, NoReturn, Union, overload
+from typing import TYPE_CHECKING, Any, ClassVar, Literal, NoReturn, Union, overload
 
 from xarray.core import utils
 from xarray.core._aggregations import DataTreeAggregations
 from xarray.core._typed_ops import DataTreeOpsMixin
 from xarray.core.alignment import align
-from xarray.core.common import TreeAttrAccessMixin, get_chunksizes
+from xarray.core.common import AccessorMixin, TreeAttrAccessMixin, get_chunksizes
 from xarray.core.coordinates import Coordinates, DataTreeCoordinates
 from xarray.core.dataarray import DataArray
 from xarray.core.dataset import Dataset, DataVariables
@@ -419,6 +419,7 @@ class DataTree(
     NamedNode["DataTree"],
     DataTreeAggregations,
     DataTreeOpsMixin,
+    AccessorMixin,
     TreeAttrAccessMixin,
     Mapping[str, "DataArray | DataTree"],
 ):
@@ -455,6 +456,7 @@ class DataTree(
     _attrs: dict[Hashable, Any] | None
     _encoding: dict[Hashable, Any] | None
     _close: Callable[[], None] | None
+    _accessors: ClassVar[set[str]] = set()
 
     __slots__ = (
         "_attrs",
diff --git a/xarray/core/extensions.py b/xarray/core/extensions.py
index c235fae000a..e517e656659 100644
--- a/xarray/core/extensions.py
+++ b/xarray/core/extensions.py
@@ -57,6 +57,7 @@ def decorator(accessor):
                 stacklevel=2,
             )
         setattr(cls, name, _CachedAccessor(name, accessor))
+        cls._accessors.add(name)
         return accessor
 
     return decorator
diff --git a/xarray/tests/test_extensions.py b/xarray/tests/test_extensions.py
index 8a52f79198d..816693c4c19 100644
--- a/xarray/tests/test_extensions.py
+++ b/xarray/tests/test_extensions.py
@@ -34,6 +34,10 @@ def __init__(self, xarray_obj):
             def foo(self):
                 return "bar"
 
+        assert "demo" in dir(xr.DataTree)
+        assert "demo" in dir(xr.Dataset)
+        assert "demo" in dir(xr.DataArray)
+
         dt: xr.DataTree = xr.DataTree()
         assert dt.demo.foo == "bar"