diff --git a/doc/source/whatsnew/v0.16.1.txt b/doc/source/whatsnew/v0.16.1.txt
index 8c49e2780ed06..3949ad4394fb1 100644
--- a/doc/source/whatsnew/v0.16.1.txt
+++ b/doc/source/whatsnew/v0.16.1.txt
@@ -79,3 +79,4 @@ Bug Fixes
 
 - Bug in ``Series.quantile`` on empty Series of type ``Datetime`` or ``Timedelta`` (:issue:`9675`)
 - Bug in ``where`` causing incorrect results when upcasting was required (:issue:`9731`)
+- Bug in ``where`` when dtype of self is datetime64 or timedelta64, but dtype of other is not
\ No newline at end of file
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index e05709d7a180f..e1a50f8b5200a 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -3323,7 +3323,8 @@ def where(self, cond, other=np.nan, inplace=False, axis=None, level=None,
                 except ValueError:
                     new_other = np.array(other)
 
-                if not (new_other == np.array(other)).all():
+                matches = (new_other == np.array(other))
+                if matches is False or not matches.all():
                     other = np.array(other)
 
                     # we can't use our existing dtype
diff --git a/pandas/core/internals.py b/pandas/core/internals.py
index 7a16fb2b6b0d7..3418295adabf5 100644
--- a/pandas/core/internals.py
+++ b/pandas/core/internals.py
@@ -1324,13 +1324,11 @@ def _try_fill(self, value):
         return value
 
     def _try_coerce_args(self, values, other):
-        """ provide coercion to our input arguments
-            we are going to compare vs i8, so coerce to floats
-            repring NaT with np.nan so nans propagate
-            values is always ndarray like, other may not be """
+        """ Coerce values and other to float64, with null values converted to
+            NaN. values is always ndarray-like, other may not be """
         def masker(v):
             mask = isnull(v)
-            v = v.view('i8').astype('float64')
+            v = v.astype('float64')
             v[mask] = np.nan
             return v
 
@@ -1342,6 +1340,8 @@ def masker(v):
             other = _coerce_scalar_to_timedelta_type(other, unit='s', box=False).item()
             if other == tslib.iNaT:
                 other = np.nan
+        elif lib.isscalar(other):
+            other = np.float64(other)
         else:
             other = masker(other)
 
@@ -1807,16 +1807,20 @@ def _try_operate(self, values):
         return values.view('i8')
 
     def _try_coerce_args(self, values, other):
-        """ provide coercion to our input arguments
-            we are going to compare vs i8, so coerce to integer
-            values is always ndarra like, other may not be """
+        """ Coerce values and other to dtype 'i8'. NaN and NaT convert to
+            the smallest i8, and will correctly round-trip to NaT if converted
+            back in _try_coerce_result. values is always ndarray-like, other
+            may not be """
         values = values.view('i8')
+
         if is_null_datelike_scalar(other):
             other = tslib.iNaT
         elif isinstance(other, datetime):
             other = lib.Timestamp(other).asm8.view('i8')
-        else:
+        elif hasattr(other, 'dtype') and com.is_integer_dtype(other):
             other = other.view('i8')
+        else:
+            other = np.array(other, dtype='i8')
 
         return values, other
 
diff --git a/pandas/tests/test_series.py b/pandas/tests/test_series.py
index e140ffd97051c..25487a081571a 100644
--- a/pandas/tests/test_series.py
+++ b/pandas/tests/test_series.py
@@ -1855,6 +1855,48 @@ def test_where_dups(self):
         expected = Series([5,11,2,5,11,2],index=[0,1,2,0,1,2])
         assert_series_equal(comb, expected)
 
+    def test_where_datetime(self):
+        s = Series(date_range('20130102', periods=2))
+        expected = Series([10, 10], dtype='datetime64[ns]')
+        mask = np.array([False, False])
+
+        rs = s.where(mask, [10, 10])
+        assert_series_equal(rs, expected)
+
+        rs = s.where(mask, 10)
+        assert_series_equal(rs, expected)
+
+        rs = s.where(mask, 10.0)
+        assert_series_equal(rs, expected)
+
+        rs = s.where(mask, [10.0, 10.0])
+        assert_series_equal(rs, expected)
+
+        rs = s.where(mask, [10.0, np.nan])
+        expected = Series([10, None], dtype='datetime64[ns]')
+        assert_series_equal(rs, expected)
+
+    def test_where_timedelta(self):
+        s = Series([1, 2], dtype='timedelta64[ns]')
+        expected = Series([10, 10], dtype='timedelta64[ns]')
+        mask = np.array([False, False])
+
+        rs = s.where(mask, [10, 10])
+        assert_series_equal(rs, expected)
+
+        rs = s.where(mask, 10)
+        assert_series_equal(rs, expected)
+
+        rs = s.where(mask, 10.0)
+        assert_series_equal(rs, expected)
+
+        rs = s.where(mask, [10.0, 10.0])
+        assert_series_equal(rs, expected)
+
+        rs = s.where(mask, [10.0, np.nan])
+        expected = Series([10, None], dtype='timedelta64[ns]')
+        assert_series_equal(rs, expected)
+
     def test_mask(self):
         s = Series(np.random.randn(5))
         cond = s > 0