diff --git a/src/blaxel/core/sandbox/sync/filesystem.py b/src/blaxel/core/sandbox/sync/filesystem.py
index b263057..eaf3af6 100644
--- a/src/blaxel/core/sandbox/sync/filesystem.py
+++ b/src/blaxel/core/sandbox/sync/filesystem.py
@@ -302,9 +302,18 @@ def _upload_with_multipart(
             for i in range(0, num_parts, MAX_PARALLEL_UPLOADS):
                 threads = []
                 results: Dict[int, Dict[str, Any]] = {}
+                exceptions: List[Exception] = []
+                results_lock = threading.Lock()
 
                 def make_upload(part_number: int, chunk: bytes):
-                    results[part_number] = self._upload_part(upload_id, part_number, chunk)
+                    try:
+                        result = self._upload_part(upload_id, part_number, chunk)
+                    except Exception as error:
+                        with results_lock:
+                            exceptions.append(error)
+                    else:
+                        with results_lock:
+                            results[part_number] = result
 
                 for j in range(MAX_PARALLEL_UPLOADS):
                     if i + j >= num_parts:
@@ -318,6 +327,8 @@ def make_upload(part_number: int, chunk: bytes):
                     t.start()
                 for t in threads:
                     t.join()
+                if exceptions:
+                    raise exceptions[0]
                 for part_number, r in results.items():
                     parts.append({"partNumber": part_number, "etag": r.get("etag")})
             parts.sort(key=lambda p: p.get("partNumber", 0))
diff --git a/tests/core/test_sandbox_filesystem.py b/tests/core/test_sandbox_filesystem.py
new file mode 100644
index 0000000..5793683
--- /dev/null
+++ b/tests/core/test_sandbox_filesystem.py
@@ -0,0 +1,31 @@
+import pytest
+
+from blaxel.core.sandbox.sync.filesystem import SyncSandboxFileSystem
+
+
+def test_sync_multipart_upload_aborts_when_part_thread_fails():
+    filesystem = object.__new__(SyncSandboxFileSystem)
+    uploaded_parts = []
+    aborted_uploads = []
+    completed_parts = []
+
+    filesystem._initiate_multipart_upload = lambda path, permissions="0644": {
+        "uploadId": "upload-1"
+    }
+
+    def upload_part(upload_id, part_number, data):
+        uploaded_parts.append(part_number)
+        if part_number == 2:
+            raise RuntimeError("part 2 failed")
+        return {"partNumber": part_number, "etag": f"etag-{part_number}"}
+
+    filesystem._upload_part = upload_part
+    filesystem._abort_multipart_upload = lambda upload_id: aborted_uploads.append(upload_id)
+    filesystem._complete_multipart_upload = lambda upload_id, parts: completed_parts.append(parts)
+
+    with pytest.raises(RuntimeError, match="part 2 failed"):
+        filesystem._upload_with_multipart("/tmp/large.bin", b"0" * (11 * 1024 * 1024))
+
+    assert 2 in uploaded_parts
+    assert aborted_uploads == ["upload-1"]
+    assert completed_parts == []