diff --git a/doc/source/whatsnew/v0.21.0.txt b/doc/source/whatsnew/v0.21.0.txt
index b6bd86bd79a1f..60a9d4435e86c 100644
--- a/doc/source/whatsnew/v0.21.0.txt
+++ b/doc/source/whatsnew/v0.21.0.txt
@@ -597,6 +597,7 @@ Groupby/Resample/Rolling
 - Bug in :func:`infer_freq` causing indices with 2-day gaps during the working week to be wrongly inferred as business daily (:issue:`16624`)
 - Bug in ``.rolling(...).quantile()`` which incorrectly used different defaults than :func:`Series.quantile()` and :func:`DataFrame.quantile()` (:issue:`9413`, :issue:`16211`)
 - Bug in ``groupby.transform()`` that would coerce boolean dtypes back to float (:issue:`16875`)
+- Bug in ``Grouper.aggregate()`` where grouping by a vector of mixed types would raise a ``TypeError`` only if the aggregating function returned a list-like object (:issue:`16916`)
 - Bug in ``Series.resample(...).apply()`` where an empty ``Series`` modified the source index and did not return the name of a ``Series`` (:issue:`14313`)
 - Bug in ``.rolling(...).apply(...)`` with a ``DataFrame`` with a ``DatetimeIndex``, a ``window`` of a timedelta-convertible and ``min_periods >= 1` (:issue:`15305`)
 - Bug in ``DataFrame.groupby`` where index and column keys were not recognized correctly when the number of keys equaled the number of elements on the groupby axis (:issue:`16859`)
diff --git a/pandas/core/groupby.py b/pandas/core/groupby.py
index a62ae40a85941..a0e842d308d8a 100644
--- a/pandas/core/groupby.py
+++ b/pandas/core/groupby.py
@@ -59,6 +59,7 @@
 from pandas.io.formats.printing import pprint_thing
 from pandas.util._validators import validate_kwargs
 
+from pandas.core.sorting import safe_sort
 import pandas.core.algorithms as algorithms
 import pandas.core.common as com
 from pandas.core.config import option_context
@@ -2897,7 +2898,7 @@ def aggregate(self, func_or_funcs, *args, **kwargs):
             except Exception:
                 result = self._aggregate_named(func_or_funcs, *args, **kwargs)
 
-            index = Index(sorted(result), name=self.grouper.names[0])
+            index = Index(safe_sort(result), name=self.grouper.names[0])
             ret = Series(result, index=index)
 
         if not self.as_index:  # pragma: no cover
diff --git a/pandas/tests/groupby/test_aggregate.py b/pandas/tests/groupby/test_aggregate.py
index efc833575843c..daa78f2ec79d8 100644
--- a/pandas/tests/groupby/test_aggregate.py
+++ b/pandas/tests/groupby/test_aggregate.py
@@ -892,3 +892,17 @@ def test_sum_uint64_overflow(self):
         expected.index.name = 0
         result = df.groupby(0).sum()
         tm.assert_frame_equal(result, expected)
+
+    def test_mixed_type_grouping(self):
+        # see gh-19616
+        expected = pd.DataFrame(data=[[[1, 1], [2, 2], [3, 3]],
+                                      [[1, 1], [2, 2], [3, 3]]],
+                                columns=['X', 'Y', 'Z'],
+                                index=pd.Index(data=[2, 'g1'],
+                                name='grouping'))
+
+        df = pd.DataFrame(data=[[1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3]],
+                          columns=list('XYZ'), index=list('qwer'))
+        df['grouping'] = ['g1', 'g1', 2, 2]
+        result = df.groupby('grouping').aggregate(lambda x: x.tolist())
+        tm.assert_frame_equal(result, expected)