The Golden Griffins (5-1), who finished 5-25 last season, have already matched that victory total in their first season for coach Jim Baron.
Billy Baron, the coach's son, made 5 of 7 shots in the first half and had 12 of his points as Canisius took a 36-30 lead at the break. He transferred from Rhode Island after last season when his father left there to take the Canisius job.
Washington scored 14 of his points in the second half. Jordan Heath scored 10 points and blocked four shots for the Golden Griffins before fouling out.
Derek Needham, with 11 points, was the only player in double figures for the Stags (4-5), who had won their last nine games against Canisius.