The veteran receiver signed as a free agent with the Lions on Thursday, two days after published reports said the former Brigham Young University star had come to terms with the Montreal Alouettes.
Collie took to Twitter on Wednesday to deny the reports.
The six-foot, 204-pound Collie spent five seasons in the NFL — four with the Indianapolis Colts, another with the New England Patriots. He was a fourth-round pick of the Colts in the 2009 NFL draft.
Collie appeared in 42 games over four seasons with the Colts, registering 173 catches for 1,845 yards and 16 TDs. He signed with New England in 2013, playing in seven regular-season games and recording six catches for 63 yards.
"Austin has an established football resume and will add depth, speed and experience to our roster," Wally Buono, the Lions vice-president of football operations, said in a statement. "He's an exciting player that I know our fans will enjoy watching this season."
Collie, 29, is a Hamilton native and joins the Lions as a national — or Canadian — player. But he comes with issues — he suffered at least three concussions during his NFL tenure.
"I'm excited to be joining the Lions and very much look forward to playing in the CFL," said Collie. "The wide-open play of the Canadian game and the passion of fans across the league is going to be a lot of fun to experience."