diff --git a/monai/data/image_reader.py b/monai/data/image_reader.py
index a85eb95c20..56ed1f9ca3 100644
--- a/monai/data/image_reader.py
+++ b/monai/data/image_reader.py
@@ -758,7 +758,7 @@ def _get_affine(self, metadata: dict, lps_to_ras: bool = True):
         affine[2, 3] = sz
 
         # 3d
-        if "lastImagePositionPatient" in metadata:
+        if "lastImagePositionPatient" in metadata and metadata[MetaKeys.SPATIAL_SHAPE][-1] > 1:
             t1n, t2n, t3n = metadata["lastImagePositionPatient"]
             n = metadata[MetaKeys.SPATIAL_SHAPE][-1]
             k1, k2, k3 = (t1n - sx) / (n - 1), (t2n - sy) / (n - 1), (t3n - sz) / (n - 1)
diff --git a/tests/data/test_init_reader.py b/tests/data/test_init_reader.py
index 169fd20a5f..bad58cd42f 100644
--- a/tests/data/test_init_reader.py
+++ b/tests/data/test_init_reader.py
@@ -19,6 +19,7 @@
 
 from monai.data import ITKReader, NibabelReader, NrrdReader, NumpyReader, PILReader, PydicomReader
 from monai.transforms import LoadImage, LoadImaged
+from monai.utils import MetaKeys
 from tests.test_utils import SkipIfNoModule
 
 
@@ -100,6 +101,40 @@ def test_nibabel_reader_avoids_eager_c_order_copy(self):
                     # (F-order) layout from nibabel should be preserved here.
                     self.assertFalse(data.flags.c_contiguous)
 
+    @SkipIfNoModule("Pydicom")
+    def test_pydicom_reader_get_affine_single_slice_with_last_position(self):
+        reader = PydicomReader()
+        metadata = {
+            "00200037": {"Value": [1.0, 0.0, 0.0, 0.0, 1.0, 0.0]},
+            "00200032": {"Value": [10.0, 20.0, 30.0]},
+            "00280030": {"Value": [0.5, 0.25]},
+            "lastImagePositionPatient": np.array([10.0, 20.0, 30.0]),
+            MetaKeys.SPATIAL_SHAPE: np.array([64, 64, 1]),
+        }
+
+        affine = reader._get_affine(metadata, lps_to_ras=False)
+
+        np.testing.assert_allclose(affine[0, 2], 0.0)
+        np.testing.assert_allclose(affine[1, 2], 0.0)
+        np.testing.assert_allclose(affine[2, 2], 1.0)
+
+    @SkipIfNoModule("Pydicom")
+    def test_pydicom_reader_get_affine_multi_slice_uses_last_position(self):
+        reader = PydicomReader()
+        metadata = {
+            "00200037": {"Value": [1.0, 0.0, 0.0, 0.0, 1.0, 0.0]},
+            "00200032": {"Value": [0.0, 0.0, 0.0]},
+            "00280030": {"Value": [1.0, 1.0]},
+            "lastImagePositionPatient": np.array([0.0, 0.0, 4.0]),
+            MetaKeys.SPATIAL_SHAPE: np.array([8, 8, 5]),
+        }
+
+        affine = reader._get_affine(metadata, lps_to_ras=False)
+
+        np.testing.assert_allclose(affine[0, 2], 0.0)
+        np.testing.assert_allclose(affine[1, 2], 0.0)
+        np.testing.assert_allclose(affine[2, 2], 1.0)
+
 
 if __name__ == "__main__":
     unittest.main()