After going undrafted at the 1998 NFL Draft, Cahoon tried out for the Tampa Bay Buccaneers before being released. He was drafted by the Montreal Alouettes in the first round (sixth overall) in the 1998 CFL Draft. He won the 90th Grey Cup, 97th Grey Cup and 98th Grey Cup with Montreal in 2002, 2009 and 2010. He was named Grey Cup Most Valuable Canadian in both 2002 and 2009. His number with the Montreal Alouettes is 86. His jersey was retired on July 29, 2016 at Percival Molson Stadium in Montréal.