Mitchell spent the 1995 season with the Scottish Claymores of the World League of American Football, having been allocated there by the New Orleans Saints, catching 11 passes for 145 yards and one touchdown.

After a failed tryout in the National Football League in 1999, Mitchell returned to the Argos and consistently put up 1,000-yard or close to 1,000-yard seasons.

In 2004, he was released by the Argonauts, and was promptly signed by the Edmonton Eskimos who he helped win the 2005 Grey Cup a season later.

On July 26, 2007, Mitchell set a new Argonaut record for career receiving yards after catching a pass from Damon Allen in a home game against the Montreal Alouettes, surpassing former record holder Paul Masotti's 8772 receiving yards.

On October 27, 2007, Mitchell surpassed 12,000 career receiving yards in the CFL against the Winnipeg Blue Bombers.