Makdessi (10-2) used a smart game plan — and stinging left jab — to pick away at Stout in a clinical 30-27, 29-28, 30-27 win.
The main event of the Bell Centre mixed martial arts card was a welterweight title fight between Montreal's Georges St-Pierre and Carlos (Natural Born Killer) Condit.
St-Pierre, the reigning 170-pound champion, has not fought since April 2011 as the result of reconstructive knee surgery. Condit won the interim title during his absence, defeating Nick Diaz in February.
Condit was booed as he was shown entering the arena on the video screens. The crowd went wild at GSP's entry, especially when the champ faked a limp before grinning and giving a thumbs-up.
A GSP win likely means a super-fight showdown with middleweight (185-pound) champion Anderson Silva. The 37-year-old Brazilian met the media before the card started, declaring his interest in meeting GSP somewhere between their two weight classes.
Stout, from London, Ont., and Montreal's Makdessi both received loud welcomes from the Bell Centre crowd.
Stout (19-8-1) pressed the action to start but Makdessi scored with some good counter-punches and stuffed some takedown attempts. Stout began to get frustrated in the second as Makdessi made him pay.
In the third, Makdessi lashed Stout in the face with a kick and Stout's face looked the worse for wear as the run wore on. Stout never stopped coming forward but he also never found the key to Makdessi.
Makdessi needed the win after two straight losses. It was also a welcome result for his brother David, whose clothing line Fear the Fighter was well-represented on the night.
There were eight Canadians on the Bell Centre card, not counting Montreal-based French middleweight Francis Carmont — one of five Tristar Gym fighters in action.
There would have been nine but Calgary middleweight Nick (The Promise) Ring was forced to pull out earlier in the day due to illness. His bout with American Costa Philippou was scrapped.
The other Canadians faced foreign opponents on the night, going 3-0 on the undercard.
Veteran Montreal middleweight Patrick (The Predator) Cote won by first-round disqualification over Italy's Alessio (Legionarius) Sakara.
The fight was stopped at 1:26 after Sakara floored Cote with elbows to the head and then nailed a dazed Cote — who was on his knees — with hammer-fists, of which eight straight were illegal blows to the back of the head.
The crowd, which had been singing "Ole, Ole, Ole" during the bout, booed as they watched replays or Sakara was shown on the video screen. Cote, who just shook his head, was rewarded with cheers.
The win was then given to Cote (19-8).
Sakara (19-10 with one no contest) apologized after the fight, saying he was caught up in the moment.
Montreal bantamweight Ivan (Pride of El Salvador) Menjivar pulled off a slick belly-down armbar to defeat Azamat Gashimov, an American-based Russian, by submission at 2:44 of the first round. As the first Canadian out on the card, Menjivar was rewarded with plenty of love from the crowd for his fourth win in five UFC fights.
Gashimov (10-2) took Menjivar (25-9) down and paid for it. Gashimov's face was contorted in pain as he tapped out in his UFC debut, his arm bent at an impossible angle.
"I let him punch me and then I submitted him," said Menjivar.
Featherweight Antonio (Pato) Carvalho (15-5) of Ajax, Ont., won a 29-28, 29-28, 28-29 split decision over former Strikeforce contender Rodrigo Damm in a bout dominated by savage leg kicks.
The first round had the crowd booing but both fighters paid a price for the action, showing visible damage on their legs. By the end of three rounds, it looked like both men had had graters scraped across their thighs repeatedly.
"I got the win but I wasn't happy with my performance," said Carvalho.
Damm (10-6) had Silva in his corner.
Lanky light-heavyweight Cyrille (The Snake) Diabate (20-8-3) showed off his ground skills in choking out Chad (The Grave Digger) Griggs at 2:24 of the first round.
Griggs, a full-time Tucson firefighter who was moving down to light-heavyweight, came out wild and Diabate floored him with a counter-right. Once the fight hit the ground, it was all Diabate. The 39-year-old bloodied up Griggs (11-3) and then locked in a rear-naked choke.
Welterweight Matt (Deep Waters) Riddle won a decision over England's John (The One) Maguire in a battle of injury replacements. Riddle (7-3 with one no contest) was returning from a 90-day marijuana suspension from UFC 149 in Calgary, which he said was the result of medicinal use.
Riddle turned heads with an acrobatic jumping spin kick thrown while Maguire (18-5) was holding the other in a takedown attempt. A crowd-pleaser who is no shrinking violet, Riddle entered the cage to Iron Butterfly's "In-A-Gadda-Da-Vida" and exited dancing to the reggae music playing over the sound system.
Darren (The Damage) Elkins ran his winning streak to four at featherweight with a decision over a game (Super) Steven Siler (21-10). Takedowns and ground superiority were the difference for Elkins (16-2), who went 1-1 as a lightweight before dropping down a weight class.