diff --git a/crates/polars-mem-engine/src/executors/sort.rs b/crates/polars-mem-engine/src/executors/sort.rs
index 4c3303dbae32..d20cbb0e0c70 100644
--- a/crates/polars-mem-engine/src/executors/sort.rs
+++ b/crates/polars-mem-engine/src/executors/sort.rs
@@ -13,10 +13,9 @@ impl SortExec {
     fn execute_impl(
         &mut self,
         state: &ExecutionState,
-        mut df: DataFrame,
+        df: DataFrame,
     ) -> PolarsResult<DataFrame> {
         state.should_stop()?;
-        df.rechunk_mut_par();
 
         let height = df.height();
 
diff --git a/py-polars/tests/unit/operations/test_sort.py b/py-polars/tests/unit/operations/test_sort.py
index 7424776e0321..621133080b85 100644
--- a/py-polars/tests/unit/operations/test_sort.py
+++ b/py-polars/tests/unit/operations/test_sort.py
@@ -1289,3 +1289,13 @@ def test_sort_by_empty_list_eval_25433() -> None:
     out = df.select(pl.col.a.list.eval(pl.element().sort_by(pl.element())))
     expected = pl.DataFrame({"a": [sorted(some_list), []]})
     assert_frame_equal(out, expected)
+
+
+def test_sort_already_sorted_no_rechunk_25733() -> None:
+    df1 = pl.DataFrame({"a": [1, 2], "b": [3, 4]})
+    df2 = pl.DataFrame({"a": [3, 4], "b": [5, 6]})
+    df = pl.concat([df1, df2], rechunk=False).with_columns(pl.col("a").set_sorted())
+    assert df.n_chunks() == 2
+
+    result = df.sort("a")
+    assert result.n_chunks() == 2  # No rechunk happened