diff --git a/pre_commit/commands/hook_impl.py b/pre_commit/commands/hook_impl.py
@@ -14,6 +14,15 @@
 Z40 = '0' * 40
 
 
+def _is_zero_oid(oid: str) -> bool:
+    """True for the all-zero OID of either supported object format.
+
+    Git SHA-1 repos use a 40-hex zero OID; SHA-256 repos use 64. Hardcoding
+    only the SHA-1 form breaks ``git push --delete`` on SHA-256 repos (#3664).
+    """
+    return len(oid) in (40, 64) and set(oid) == {'0'}
+
+
 def _run_legacy(
         hook_type: str,
         hook_dir: str | None,
@@ -128,9 +137,9 @@ def _pre_push_ns(
     for line in stdin.decode().splitlines():
         parts = line.rsplit(maxsplit=3)
         local_branch, local_sha, remote_branch, remote_sha = parts
-        if local_sha == Z40:
+        if _is_zero_oid(local_sha):
             continue
-        elif remote_sha != Z40 and _rev_exists(remote_sha):
+        elif not _is_zero_oid(remote_sha) and _rev_exists(remote_sha):
             return _ns(
                 'pre-push', color,
                 from_ref=remote_sha, to_ref=local_sha,

diff --git a/tests/commands/hook_impl_test.py b/tests/commands/hook_impl_test.py
@@ -384,3 +384,27 @@ def test_hook_impl_main_runs_hooks(cap_out, tempdir_factory, store):
 Block if "DO NOT COMMIT" is found....................(no files to check)Skipped
 '''
     assert cap_out.get() == expected
+
+
+def test_is_zero_oid():
+    assert hook_impl._is_zero_oid('0' * 40)
+    assert hook_impl._is_zero_oid('0' * 64)
+    assert not hook_impl._is_zero_oid('0' * 39)
+    assert not hook_impl._is_zero_oid('0' * 41)
+    assert not hook_impl._is_zero_oid('0' * 63)
+    assert not hook_impl._is_zero_oid('0' * 65)
+    assert not hook_impl._is_zero_oid('1' + '0' * 39)
+    assert not hook_impl._is_zero_oid('')
+
+
+def test_run_ns_pre_push_deleting_branch_sha256(push_example):
+    """Deletion pushes use a 64-zero OID on SHA-256 repos (#3664)."""
+    src, src_head, clone, _ = push_example
+    z64 = '0' * 64
+
+    with contextlib.chdir(clone):
+        args = ('origin', src)
+        stdin = f'(delete) {z64} refs/heads/b {src_head}'.encode()
+        ns = hook_impl._run_ns('pre-push', False, args, stdin)
+
+    assert ns is None