diff --git a/doc/source/whatsnew/v0.19.0.txt b/doc/source/whatsnew/v0.19.0.txt
index 0b9695125c0a9..5c4c1126cb078 100644
--- a/doc/source/whatsnew/v0.19.0.txt
+++ b/doc/source/whatsnew/v0.19.0.txt
@@ -614,3 +614,4 @@ Bug Fixes
 - Bug in ``groupby`` with ``as_index=False`` returns all NaN's when grouping on multiple columns including a categorical one (:issue:`13204`)
 
 - Bug where ``pd.read_gbq()`` could throw ``ImportError: No module named discovery`` as a result of a naming conflict with another python package called apiclient  (:issue:`13454`)
+- Bug in ``pandas.Series.str.zfill``, when ``width`` was not of integer type no ``TypeError`` was raised, which resulted in a series with all NaN values (:issue:`13598`)
\ No newline at end of file
diff --git a/pandas/core/strings.py b/pandas/core/strings.py
index 6ec28f9735850..3150fc5d0143a 100644
--- a/pandas/core/strings.py
+++ b/pandas/core/strings.py
@@ -8,7 +8,8 @@
                                  is_object_dtype,
                                  is_string_like,
                                  is_list_like,
-                                 is_scalar)
+                                 is_scalar,
+                                 is_integer)
 from pandas.core.common import _values_from_object
 
 from pandas.core.algorithms import take_1d
@@ -914,6 +915,10 @@ def str_pad(arr, width, side='left', fillchar=' '):
     if len(fillchar) != 1:
         raise TypeError('fillchar must be a character, not str')
 
+    if not is_integer(width):
+        msg = 'width must be of integer type, not {0}'
+        raise TypeError(msg.format(type(width).__name__))
+
     if side == 'left':
         f = lambda x: x.rjust(width, fillchar)
     elif side == 'right':
diff --git a/pandas/tests/test_strings.py b/pandas/tests/test_strings.py
index 4d23bed620265..2a4fc8b2db5c9 100644
--- a/pandas/tests/test_strings.py
+++ b/pandas/tests/test_strings.py
@@ -1603,6 +1603,15 @@ def test_pad_fillchar(self):
                                    "fillchar must be a character, not int"):
             result = values.str.pad(5, fillchar=5)
 
+    def test_pad_width(self):
+        values = Series(['1', '22', 'a', 'bb'])
+        s = Series(values)
+
+        for f in ['center', 'ljust', 'rjust', 'zfill', 'pad']:
+            with tm.assertRaisesRegexp(TypeError,
+                                       "width must be of integer type, not*"):
+                getattr(s.str, f)('f')
+
     def test_translate(self):
 
         def _check(result, expected):