A heat exchanger for a motor vehicle includes a fin/tube block with flat tubes which are provided on opposite sides with tube ends. The tube ends are widened such that transversely extending, mutually adjacent wall sections of the tube ends flatly adjoin one another and the tube ends of a row are aligned with one another. One flow box is placed on the tube ends on each side of the fin/tube block. Each of the flow boxes ends flush with corresponding longitudinally extending wall sections of the tube ends. The transversely extending, mutually adjacent wall sections of the tube ends adjoin one another in a form-locking manner.