diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 888507a529687..85fbde799dae7 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -1832,15 +1832,31 @@ def __contains__(self, key):
             return False
 
     _index_shared_docs['contains'] = """
-        return a boolean if this key is IN the index
+        Return a boolean if key is in the index.
+
+        This function returns True if key is in the index and
+        returns False if key is not in index.
 
         Parameters
         ----------
-        key : object
+        key : immutable object
+            Key to be searched.
 
         Returns
         -------
-        boolean
+        bool
+            Result of the key search.
+
+        Notes
+        -----
+            CategoricalIndex is a sub-class of Index.
+
+        Examples
+        --------
+        >>> pd.CategoricalIndex([2000, 2001, 2012]).contains(2001)
+        True
+        >>> pd.CategoricalIndex([2000, 2001, 2012]).contains(2222)
+        False
         """
 
     @Appender(_index_shared_docs['contains'] % _index_doc_kwargs)