diff --git a/doc/changes/dev/13618.notable.rst b/doc/changes/dev/13618.notable.rst
new file mode 100644
index 00000000000..10202f8c55a
--- /dev/null
+++ b/doc/changes/dev/13618.notable.rst
@@ -0,0 +1 @@
+Clarify average EEG reference behavior in documentation for add_reference_channels.
\ No newline at end of file
diff --git a/mne/channels/channels.py b/mne/channels/channels.py
index c1a3d462525..c8ee5f74d57 100644
--- a/mne/channels/channels.py
+++ b/mne/channels/channels.py
@@ -812,6 +812,12 @@ def add_reference_channels(self, ref_channels):
         -------
         inst : same type as the input data
                The modified instance.
+
+        note:: If you are adding a new reference channel to data that
+                will eventually be used with an average reference,
+                you should also call :meth:`mne.io.Raw.set_eeg_reference`
+                (or the equivalent Epochs/Evoked method) to ensure the
+                mathematical reference is updated correctly.
         """
         return add_reference_channels(self, ref_channels, copy=False)