Condon, a native of Holliston, Massachusetts, was never drafted by an NHL team. After playing four seasons at Princeton University and earning Second Team All-Ivy League honors as a senior, he played on tryout contracts with Ontario of the ECHL and Houston of the American Hockey League at the end of the 2012-13 season, then was signed by the Montreal Canadiens on May 8, 2013.
After spending the next two seasons in the minors, Condon made his NHL debut with the Canadiens on Oct. 11, 2015, finishing with 20 saves in a 3-1 victory against the Ottawa Senators. After starter Carey Price went down with a knee injury in late November, Condon played in 55 games (51 starts), finishing 21-25-6 and tying John Gibson of the Anaheim Ducks for the NHL lead for wins among rookies. Condon's biggest victory came when he made 27 saves in a 5-1 victory against the Boston Bruins at the 2016 Winter Classic at Gillette Stadium in Foxborough, Massachusetts.