diff --git a/py-polars/polars/expr/string.py b/py-polars/polars/expr/string.py
index 96caa774aafb..695d0cba55fd 100644
--- a/py-polars/polars/expr/string.py
+++ b/py-polars/polars/expr/string.py
@@ -854,6 +854,11 @@ def zfill(self, length: int) -> Expr:
         --------
         pad_start
 
+        Notes
+        -----
+        This method is intended for padding numeric strings. If your data contains
+        non-ASCII characters, use :func:`pad_start` instead.
+
         Examples
         --------
         >>> df = pl.DataFrame({"a": [-1, 123, 999999, None]})
diff --git a/py-polars/polars/series/string.py b/py-polars/polars/series/string.py
index 57e613c04c64..1b8d29d2d693 100644
--- a/py-polars/polars/series/string.py
+++ b/py-polars/polars/series/string.py
@@ -1355,6 +1355,11 @@ def zfill(self, length: int) -> Series:
         --------
         pad_start
 
+        Notes
+        -----
+        This method is intended for padding numeric strings. If your data contains
+        non-ASCII characters, use :func:`pad_start` instead.
+
         Examples
         --------
         >>> s = pl.Series([-1, 123, 999999, None])