diff --git a/py-polars/polars/dataframe/frame.py b/py-polars/polars/dataframe/frame.py
index a5295cf61920..cefa6c909b92 100644
--- a/py-polars/polars/dataframe/frame.py
+++ b/py-polars/polars/dataframe/frame.py
@@ -4181,6 +4181,8 @@ def filter(
 
         The original order of the remaining rows is preserved.
 
+        Rows where the filter does not evaluate to True are discarded, including nulls.
+
         Parameters
         ----------
         predicates
diff --git a/py-polars/polars/expr/expr.py b/py-polars/polars/expr/expr.py
index aaf57bf9210f..94dc014bede4 100644
--- a/py-polars/polars/expr/expr.py
+++ b/py-polars/polars/expr/expr.py
@@ -4560,6 +4560,9 @@ def filter(
 
         The original order of the remaining elements is preserved.
 
+        Elements where the filter does not evaluate to True are discarded, including
+        nulls.
+
         Mostly useful in an aggregation context. If you want to filter on a DataFrame
         level, use `LazyFrame.filter`.
 
diff --git a/py-polars/polars/lazyframe/frame.py b/py-polars/polars/lazyframe/frame.py
index 68bf98379a68..a176cc1b3324 100644
--- a/py-polars/polars/lazyframe/frame.py
+++ b/py-polars/polars/lazyframe/frame.py
@@ -2865,6 +2865,8 @@ def filter(
 
         The original order of the remaining rows is preserved.
 
+        Rows where the filter does not evaluate to True are discarded, including nulls.
+
         Parameters
         ----------
         predicates
diff --git a/py-polars/polars/series/series.py b/py-polars/polars/series/series.py
index 4f7c5e58fa6d..d5d777549643 100644
--- a/py-polars/polars/series/series.py
+++ b/py-polars/polars/series/series.py
@@ -3177,6 +3177,9 @@ def filter(self, predicate: Series | list[bool]) -> Self:
 
         The original order of the remaining elements is preserved.
 
+        Elements where the filter does not evaluate to True are discarded, including
+        nulls.
+
         Parameters
         ----------
         predicate