diff --git a/doc/source/whatsnew/v0.22.0.txt b/doc/source/whatsnew/v0.22.0.txt
index 6dc730cae37f7..73ec9e0d5391a 100644
--- a/doc/source/whatsnew/v0.22.0.txt
+++ b/doc/source/whatsnew/v0.22.0.txt
@@ -26,6 +26,7 @@ Other Enhancements
 - :func:`pandas.tseries.frequencies.to_offset` now accepts leading '+' signs e.g. '+1h'. (:issue:`18171`)
 - :class:`pandas.io.formats.style.Styler` now has method ``hide_index()`` to determine whether the index will be rendered in ouptut (:issue:`14194`)
 - :class:`pandas.io.formats.style.Styler` now has method ``hide_columns()`` to determine whether columns will be hidden in output (:issue:`14194`)
+- Improved wording of ValueError raised in :func:`Timestamp.tz_localize` function
 
 .. _whatsnew_0220.api_breaking:
 
diff --git a/pandas/_libs/tslib.pyx b/pandas/_libs/tslib.pyx
index e4c065202a6ef..63fc84c9d7972 100644
--- a/pandas/_libs/tslib.pyx
+++ b/pandas/_libs/tslib.pyx
@@ -1445,10 +1445,8 @@ cpdef array_with_unit_to_datetime(ndarray values, unit, errors='coerce'):
             else:
 
                 if is_raise:
-                    raise ValueError("non convertible value {0}"
-                                     "with the unit '{1}'".format(
-                                         val,
-                                         unit))
+                    raise ValueError("unit='{0}' not valid with non-numerical "
+                                     "val='{1}'".format(unit, val))
                 if is_ignore:
                     raise AssertionError