diff --git a/src/zarr/core/array.py b/src/zarr/core/array.py
index 6b20ee950d..28b381c13d 100644
--- a/src/zarr/core/array.py
+++ b/src/zarr/core/array.py
@@ -1444,50 +1444,50 @@ def _iter_shard_coords(
             selection_shape=selection_shape,
         )
 
-    def _iter_shard_keys(
+    def _iter_chunk_regions(
         self, *, origin: Sequence[int] | None = None, selection_shape: Sequence[int] | None = None
-    ) -> Iterator[str]:
+    ) -> Iterator[tuple[slice, ...]]:
         """
-        Iterate over the keys of the stored objects supporting this array.
+        Iterate over the regions spanned by each chunk.
 
         Parameters
         ----------
         origin : Sequence[int] | None, default=None
             The origin of the selection relative to the array's chunk grid.
         selection_shape : Sequence[int] | None, default=None
-            The shape of the selection in shard grid coordinates.
+            The shape of the selection in chunk grid coordinates.
 
         Yields
         ------
-        key: str
-            The storage key of each chunk in the selection.
+        region: tuple[slice, ...]
+            A tuple of slice objects representing the region spanned by each chunk in the selection.
         """
-        # Iterate over the coordinates of chunks in chunk grid space.
-        return _iter_shard_keys(
+        return _iter_chunk_regions(
             array=self,
             origin=origin,
             selection_shape=selection_shape,
         )
 
-    def _iter_chunk_regions(
+    def _iter_shard_keys(
         self, *, origin: Sequence[int] | None = None, selection_shape: Sequence[int] | None = None
-    ) -> Iterator[tuple[slice, ...]]:
+    ) -> Iterator[str]:
         """
-        Iterate over the regions spanned by each chunk.
+        Iterate over the keys of the stored objects supporting this array.
 
         Parameters
         ----------
         origin : Sequence[int] | None, default=None
             The origin of the selection relative to the array's chunk grid.
         selection_shape : Sequence[int] | None, default=None
-            The shape of the selection in chunk grid coordinates.
+            The shape of the selection in shard grid coordinates.
 
         Yields
         ------
-        region: tuple[slice, ...]
-            A tuple of slice objects representing the region spanned by each chunk in the selection.
+        key: str
+            The storage key of each chunk in the selection.
         """
-        return _iter_chunk_regions(
+        # Iterate over the coordinates of chunks in chunk grid space.
+        return _iter_shard_keys(
             array=self,
             origin=origin,
             selection_shape=selection_shape,
@@ -1499,6 +1499,8 @@ def _iter_shard_regions(
         """
         Iterate over the regions spanned by each shard.
 
+        If no shards are present, then it will fall back on chunks.
+
         Parameters
         ----------
         origin : Sequence[int] | None, default=None
@@ -2643,6 +2645,9 @@ def _iter_shard_coords(
         ranging from `[origin, origin selection_shape]`, where the upper bound is exclusive as
         per python indexing conventions.
 
+        If no shard grid space is available, e.g., like in zarr version 2, the method will fall back
+        to chunk grid space.
+
         Parameters
         ----------
         origin : Sequence[int] | None, default=None
@@ -2683,6 +2688,8 @@ def _iter_shard_regions(
         """
         Iterate over the regions spanned by each shard.
 
+        If no shard is present, then it will fall back on chunks.
+
         Parameters
         ----------
         origin : Sequence[int] | None, default=None
@@ -5396,7 +5403,9 @@ def _iter_shard_coords(
     chunk_coords: tuple[int, ...]
         The coordinates of each shard in the selection.
     """
-    return _iter_grid(array._shard_grid_shape, origin=origin, selection_shape=selection_shape)
+    if array._shard_grid_shape:
+        return _iter_grid(array._shard_grid_shape, origin=origin, selection_shape=selection_shape)
+    return _iter_grid(array._chunk_grid_shape, origin=origin, selection_shape=selection_shape)
 
 
 def _iter_shard_keys(
@@ -5437,7 +5446,8 @@ def _iter_shard_regions(
     """
     Iterate over the regions spanned by each shard.
 
-    These are the smallest regions of the array that are safe to write concurrently.
+    These are the smallest regions of the array that are safe to write concurrently. If no shards
+    are present it will fall back on chunks.
 
     Parameters
     ----------