diff --git a/doc/source/whatsnew/v1.0.0.rst b/doc/source/whatsnew/v1.0.0.rst
index 8c1ce1195369d..5a10c01e36608 100644
--- a/doc/source/whatsnew/v1.0.0.rst
+++ b/doc/source/whatsnew/v1.0.0.rst
@@ -415,6 +415,7 @@ Other
 - Fix corrupted error message when calling ``pandas.libs._json.encode()`` on a 0d array (:issue:`18878`)
 - Fix :class:`AbstractHolidayCalendar` to return correct results for
   years after 2030 (now goes up to 2200) (:issue:`27790`)
+- :meth:`IndexOpsMixin._map_values` ABCSeries mapper maps unmapped categories to "" instead of NaN 
 
 
 .. _whatsnew_1000.contributors:
diff --git a/pandas/core/base.py b/pandas/core/base.py
index 5ae3926952a67..ede0c6cfc5a62 100644
--- a/pandas/core/base.py
+++ b/pandas/core/base.py
@@ -1267,7 +1267,7 @@ def _map_values(self, mapper, na_action=None):
                 values = self.values
 
             indexer = mapper.index.get_indexer(values)
-            new_values = algorithms.take_1d(mapper._values, indexer)
+            new_values = algorithms.take_1d(mapper._values, indexer, fill_value="")
 
             return new_values
 
diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index 0dc6d24202c34..fe01436b83d8a 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -1129,7 +1129,7 @@ def test_map_dictlike(self, indices, mapper):
     )
     def test_map_with_non_function_missing_values(self, mapper):
         # GH 12756
-        expected = Index([2.0, np.nan, "foo"])
+        expected = Index([2.0, "", "foo"])
         result = Index([2, 1, 0]).map(mapper)
 
         tm.assert_index_equal(expected, result)