"Michael Sam is a very good football player, and that's the reason we signed him," Popp said of Sam, who is openly gay. "He's an outstanding pass-rusher."
Sam, a free-agent, agreed to a two-year deal. The 25-year-old is to be introduced at a news conference in Montreal on Tuesday and report to training camp the following day.
"I am very excited and proud to join the Montreal Alouettes and want to thank team owner Robert Wetenhall, general manager Jim Popp and head coach Tom Higgins for this opportunity," Sam said Friday in a statement. "I cannot wait to put on the pads, get back on the field and work hard each and every day with my teammates to bring a Grey Cup to the great fans here in Montreal."
The Galveston, Texas, native became a sensation when he came out before last year's NFL draft, and his NFL jerseys were an instant best-seller.
When he was picked in the seventh round by St. Louis, President Barack Obama publicly congratulated Sam and the Rams, who made him the first openly gay player to be drafted for their courage.
CFL commissioner Jeffrey Orridge did the same on Friday.
"Congratulations to the Montreal Alouettes on the signing of Michael Sam," Orridge said in a statement. "Our players come to us from different places, different walks of life and ultimately they take different paths to get to our fields.
"Today is another indication of how open and progressive the CFL is — consistent with our rich and storied history of great football tradition."
"Michael Sam is a football player that obviously Jim Popp believes can help their team," added B.C. Lions general manager Wally Buono. "He's no different than any other player that we sign that has U.S. roots. He is a football player that I think can be a rush end. The fact that he's had notoriety of other sorts in my mind has nothing to do with him entering into our league."
Not blind to Sam's celebrity status, the team immediately put his No. 94 Alouettes jersey on sale on their website for $139.95.
Sam was cut by the Rams after training camp last year. He joined the Dallas Cowboys' practice roster but was waived in October. He took another shot at landing an NFL job by attending this year's veterans combine, with no luck.
The Alouettes had Sam on their negotiation list and Popp said he was in contact with him all along. The six-foot-two 260-pound Sam finally accepted a contract after completing his commitment to "Dancing With The Stars."
Popp said the key to landing him was patience.
"Each time he was let go there were discussions," he said. "He wanted to give it one last shot at the combine."
Popp said Sam was considered a "tweener" by NFL clubs, not quite the right body type to be a defensive end or an outside linebacker for that league.
But he may fit perfectly in the CFL. Popp feels he can follow a similar path to Cam Wake, who was converted from linebacker to rush end when he joined the B.C. Lions in 2007.
Wake had 40 sacks and was named CFL defensive player of the year in each of his two seasons with the Lions before signing with the Miami Dolphins, where he has had a successful NFL career.
"If he proves (NFL) people wrong it would be great for us and I think he can do it," said Popp.
Sam played four seasons for the University of Missouri Tigers in the NCAA, where he had 123 total tackles, 21 sacks and two interceptions.
In his last year with Missouri he helped the Tigers beat Oklahoma State in the Cotton Bowl.