Byron Dafoe was drafted 35th overall in the 1989 NHL Entry Draft by the Washington Capitals. He played Junior A hockey with Juan de Fuca of the BCJHL and joined the WHL's Portland Winter Hawks in 1988-89, winning 29 games as a rookie. In the subsequent playoffs, he appeared in 18 games, more than any other goaltender and in 1989-90, Dafoe played in 40 games and went 14-21-3 before being traded to the Prince Albert Raiders in 1990-91.
In 1991-92, Dafoe turned pro and played for the AHL's Baltimore Skipjacks, New Haven Nighthawks and the ECHL's Hampton Roads Admirals. It would be three years before he would make his NHL debut, with one minute of relief goaltending on November 11, 1992 against the New York Rangers. In 1993-94, Dafoe played five games and earned his first win on March 31 against the Chicago Blackhawks.
Dafoe's career took a monumental turn for the better on July 8, 1995 when he was traded, along with Dmitri Khristich, to the Los Angeles Kings for a pair of draft picks. That year, Dafoe shared the goaltending duties in L.A. with Kelly Hrudey. During his time with the Kings, other NHL teams had the opportunity to see that he was in fact a legitimate starting NHL goaltender.
Once again Dafoe and his trade partner Dmitri Khristich were sent packing, this time to the Boston Bruins on August 29, 1997, for Jozef Stumpel, Sandy Moger and a fourth-round draft pick. In that first season with the Bruins, he played 65 games and posted 30 wins, six shutouts and a 2.24 GAA. He became a fan favourite in Beantown and was considered an instrumental force in leading Boston to a 30-point improvement in the standings. The 1998-99 season was even better for Dafoe, who notched an impressive 1.99 GAA while leading the league with ten shutouts with a 32-23-11 record. That performance earned him Second Team All-Star laurels.
In 1999-00, Dafoe was limited to just 41 games due to a knee injury. In the 2000-01 campaign he came back strong, going 22-14-7 with a 2.39 GAA. Following an early exit in the 2002 playoffs, Dafoe was a holdout in 2002-03 and subsequently was dealt to the Atlanta Thrahsers.