diff --git a/doc/source/indexing.rst b/doc/source/indexing.rst
index 0a6691936d97d..1ea6662a4edb0 100644
--- a/doc/source/indexing.rst
+++ b/doc/source/indexing.rst
@@ -1467,6 +1467,10 @@ with duplicates dropped.
    idx1.symmetric_difference(idx2)
    idx1 ^ idx2
 
+.. note::
+
+   The resulting index from a set operation will be sorted in ascending order.
+
 Missing values
 ~~~~~~~~~~~~~~