Wille deWit was one of Canada's most outstanding amateur boxers, with an amateur record of 67–12 that included gold at the 1982 Commonwealth Games, the North American amateur heavyweight championship (1982, 1983) and the world amateur heavyweight title (1983, 1984). At the 1984 Olympic Games in Los Angeles he lost the gold medal match to Henry Tillman of the US and had to settle for Olympic silver. He turned professional after the Games and in October 1984 began to train and fight out of Burnet, Texas. From 1986 to 1988, he was Canadian professional heavyweight champion, defeating Ken Lakusta, Conroy Nelson and Tony Morrison. He retired from the sport at age 27, with a professional record of 21 wins, one loss (against American Bert Cooper) and one draw. In his last match, he defeated Olympic champion Henry Tillman.

In 1994, deWit earned a law degree from the University of Alberta. In March 2017, after over 20 years in the legal profession, he was appointed a Court of Queen’s Bench judge.