diff --git a/src/scippnexus/nxdata.py b/src/scippnexus/nxdata.py
index 38d58550..feaa22a3 100644
--- a/src/scippnexus/nxdata.py
+++ b/src/scippnexus/nxdata.py
@@ -110,6 +110,10 @@ def _init_field_dims(self, name: str, field: Field | Group) -> None:
             # len(dims).
             shape = _squeeze_trailing(dims, field.dataset.shape)
             field.sizes = dict(zip(dims, shape, strict=False))
+        elif name in self._aux_signals:
+            # Auxiliary signals are allowed to have dimensions unrelated to the
+            # primary signal. Keep the field's fallback dimensions in that case.
+            return
         elif self._valid:
             s1 = self._signal.sizes
             s2 = field.sizes
@@ -376,7 +380,13 @@ def _assemble_as_data(
             signals = {self._signal_name: da}
             signals.update(aux)
             if all(isinstance(v, sc.Variable | sc.DataArray) for v in signals.values()):
-                return sc.Dataset(signals)
+                try:
+                    return sc.Dataset(signals)
+                except sc.DimensionError:
+                    # A Dataset requires matching item dimensionality. NeXus permits
+                    # auxiliary signals on unrelated dimensions, so retain those as
+                    # separate DataGroup entries instead.
+                    pass
             return sc.DataGroup(signals)
         return da
 
diff --git a/tests/nxdata_test.py b/tests/nxdata_test.py
index 2567f699..5621fb69 100644
--- a/tests/nxdata_test.py
+++ b/tests/nxdata_test.py
@@ -276,6 +276,26 @@ def test_auxiliary_signal_causes_load_as_dataset(h5root) -> None:
     assert_identical(data[...], sc.Dataset({'signal': signal, 'xx': aux}))
 
 
+def test_auxiliary_signal_with_different_dims_loads_as_data_group(h5root) -> None:
+    signal = sc.array(dims=['tof'], unit='counts', values=[1, 2, 3])
+    frame_total = sc.array(dims=['frame'], unit='counts', values=[4, 5])
+    data = snx.create_class(h5root, 'data1', NXdata)
+    data.attrs['axes'] = signal.dims
+    data.attrs['signal'] = 'signal'
+    data.attrs['auxiliary_signals'] = ['frame_total']
+    snx.create_field(data, 'signal', signal)
+    snx.create_field(data, 'frame_total', frame_total)
+
+    loaded = snx.Group(data, definitions=snx.base_definitions())[...]
+
+    assert isinstance(loaded, sc.DataGroup)
+    assert_identical(loaded['signal'], sc.DataArray(signal))
+    assert_identical(
+        loaded['frame_total'],
+        sc.array(dims=['dim_0'], unit='counts', values=[4, 5]),
+    )
+
+
 def test_NXlog_data_is_loaded_as_time_dependent_data_array(nxroot) -> None:
     da = sc.DataArray(
         data=sc.array(dims=['time'], unit='K', values=[1, 2, 3]),