diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 9e57579ddfc05..5e3b71a7d88fa 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -3168,7 +3168,8 @@ def insert(self, loc, column, value, allow_duplicates=False):
     def assign(self, **kwargs):
         r"""
         Assign new columns to a DataFrame, returning a new object
-        (a copy) with all the original columns in addition to the new ones.
+        (a copy) with the new columns added to the original ones.
+        Existing columns that are re-assigned will be overwritten.
 
         Parameters
         ----------