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.
Forward Kennedy Meeks, who has averaged 9.4 points and 6.5 rebounds at North Carolina, has pulled out of the NBA draft and will return to the Tar Heels.
Cal big man Ivan Rabb could have been selected in the top 10 of the NBA draft. Instead, he's returning to Berkeley to make himself, and the Golden Bears, stronger.
Devin Williams' decision last month to sign with an agent and enter the NBA draft has left West Virginia in a tough spot.