Portwich also won sixteen medals at the ICF Canoe Sprint World Championships with thirteen golds (K-2 500 m: 1990, 1991, 1995; K-2 5000 m: 1989, 1990, 1991, 1993; K-4 500 m: 1987, 1990, 1991, 1993, 1994, 1995), two silvers (K-4 200 m: 1994, 1995), and a bronze (K-2 500 m: 1993).