diff --git a/mne/fixes.py b/mne/fixes.py
index 2aed20492ec..070d4125d18 100644
--- a/mne/fixes.py
+++ b/mne/fixes.py
@@ -720,3 +720,16 @@ def minimum_phase(h, method="homomorphic", n_fft=None, *, half=True):
 
     n_out = (n_half + len(h) % 2) if half else len(h)
     return h_minimum[:n_out]
+
+
+# SciPy 1.15 deprecates sph_harm for sph_harm_y and using it will trigger a
+# DeprecationWarning. This is a backport of the new function for older SciPy versions.
+def sph_harm_y(n, m, theta, phi, *, diff_n=0):
+    """Wrap scipy.special.sph_harm for sph_harm_y."""
+    # Can be removed once we no longer support scipy < 1.15.0
+    from scipy import special
+
+    if "sph_harm_y" in special.__dict__:
+        return special.sph_harm_y(n, m, theta, phi, diff_n=diff_n)
+    else:
+        return special.sph_harm(m, n, phi, theta)
diff --git a/mne/preprocessing/maxwell.py b/mne/preprocessing/maxwell.py
index 2c7e4e84b00..789c8520f05 100644
--- a/mne/preprocessing/maxwell.py
+++ b/mne/preprocessing/maxwell.py
@@ -10,7 +10,7 @@
 
 import numpy as np
 from scipy import linalg
-from scipy.special import lpmv, sph_harm_y
+from scipy.special import lpmv
 
 from .. import __version__
 from .._fiff.compensator import make_compensator
@@ -24,7 +24,7 @@
 from ..annotations import _annotations_starts_stops
 from ..bem import _check_origin
 from ..channels.channels import _get_T1T2_mag_inds, fix_mag_coil_types
-from ..fixes import _safe_svd, bincount
+from ..fixes import _safe_svd, bincount, sph_harm_y
 from ..forward import _concatenate_coils, _create_meg_coils, _prep_meg_channels
 from ..io import BaseRaw, RawArray
 from ..surface import _normalize_vectors
diff --git a/mne/preprocessing/tests/test_maxwell.py b/mne/preprocessing/tests/test_maxwell.py
index 0c9ec56b8c5..f5e816258f8 100644
--- a/mne/preprocessing/tests/test_maxwell.py
+++ b/mne/preprocessing/tests/test_maxwell.py
@@ -11,7 +11,6 @@
 import pytest
 from numpy.testing import assert_allclose, assert_array_equal
 from scipy import sparse
-from scipy.special import sph_harm_y
 
 import mne
 from mne import compute_raw_covariance, concatenate_raws, pick_info, pick_types
@@ -19,6 +18,7 @@
 from mne.annotations import _annotations_starts_stops
 from mne.chpi import filter_chpi, read_head_pos
 from mne.datasets import testing
+from mne.fixes import sph_harm_y
 from mne.forward import _prep_meg_channels, use_coil_def
 from mne.io import (
     BaseRaw,
diff --git a/mne/transforms.py b/mne/transforms.py
index b6632bbb41b..7072ea25124 100644
--- a/mne/transforms.py
+++ b/mne/transforms.py
@@ -12,14 +12,13 @@
 import numpy as np
 from scipy import linalg
 from scipy.spatial.distance import cdist
-from scipy.special import sph_harm_y
 
 from ._fiff.constants import FIFF
 from ._fiff.open import fiff_open
 from ._fiff.tag import read_tag
 from ._fiff.write import start_and_end_file, write_coord_trans
 from .defaults import _handle_default
-from .fixes import _get_img_fdata, jit
+from .fixes import _get_img_fdata, jit, sph_harm_y
 from .utils import (
     _check_fname,
     _check_option,