Canadian welterweight Rory (Red King) MacDonald, ranked No. 2 among 170-pound contenders, faces No. 5 Hector Lombard, a former Cuban judo Olympian, in the co-main event at the Bell Centre.
UFC president Dana White announced the Montreal card via a TV appearance Saturday evening.
Dillashaw won the 135-pound title off Barao at UFC 173 in May 2014, dominating the Brazilian before stopping him in the fifth round. The loss snapped a 22-fight winning streak and 34-fight unbeaten streak for Barao (35-2 with one no contest) dating back to his pro debut in April 2005.
The two were supposed to meet three months later in a rematch at UFC 177 but Barao was scratched on the eve of the bout after passing out due to his weight cut.
Dillashaw (12-2) beat Joe Soto instead, again by fifth-round stoppage.
UFC 186 marks the first UFC show in Montreal since March 2013 when then-welterweight champion Georges St-Pierre defeated Nick Diaz at UFC 158.
Montreal and Toronto were both to have hosted shows in 2014 but the UFC moved them to Las Vegas — UFC 178 (originally slated for Toronto) in September and UFC 181 (Montreal) in December.
MacDonald (18-2) had hoped to be fighting newly crowned (Ruthless) Robbie Lawler for the welterweight title but the UFC, which had promised him the next shot at the championship, elected instead to stage a third fight between Lawler and Johny (Bigg Rigg) Hendricks.
With Lawler opting not to fight until the summer, that leaves No. 1 Hendricks and No. 2 MacDonald with time on their hands.
Hendricks, who beat Lawler the first time they met to decide ownership of the title vacated by Montreal's St-Pierre as champion, is scheduled to face No. 6 Matt (The Immortal) Brown at UFC 195 in March.
Lombard (35-4-1 with one no contest) asked to meet MacDonald after comprehensively beating Josh (The People's Warrior) Burkman at UFC 181 last month.
The 36-year-old Lombard, a five-foot-11 slab of muscle who competed for Cuba in judo at the 2000 Olympics, has beaten Nate (The Great) Marquardt, Jake Shields and Burkman since dropping down to 170 pounds.
The former Bellator middleweight champion, who trains out of American Top Team in Florida, has black belts in judo and Brazilian jiu-jitsu. MacDonald also has his BJJ black belt.
The Montreal card will also see former light-heavyweight champion Quinton (Rampage) Jackson return to UFC action against Brazil's Fabio Maldonado (22-7).
Jackson (32-10) won three fights in Bellator since leaving the UFC after a January 2013 loss to Glover Teixeira, his third straight defeat in the Octagon. Maldonado, a 34-year-old former pro boxer ranked 13th among 205-pound contenders, has won four of his last five UFC bouts.
C.B. (The Doberman) Dollaway (16-7) takes on England's Michael Bisping (26-7) in a battle of middleweights coming off losses.
Dollaway, ranked 10th among 185-pound contenders, suffered a first-round knockout at the hands of Lyoto (The Dragon) Machida in December. No. 9 Bisping was submitted in the second round by Luke Rockhold in November.
Montreal's Patrick (The Predator) Cote (21-9) faces Joe (Diesel) Riggs (40-15) in a matchup of veteran welterweights.
In other UFC 186 action, Montreal's Valerie (Trouble) Letourneau (6-3) meets Hamilton's Jessica (Ragin) Rakoczy (1-4) in a women's strawweight bout and lightweight David (BullDawg) Michaud (8-1) faces Montreal's Olivier Aubin-Mercier (6-1).
The UFC has announced three to five shows in Canada in 2015 but has yet to flesh out the rest of the schedule.
The last show in Canada was a televised Fight Night card last October in Halifax. The last pay-per-view was UFC 174 in June 2014 in Vancouver.
The UFC has held 17 shows in Canada, with stops in Calgary, Halifax, Montreal, Quebec City, Toronto, Winnipeg and Vancouver.
The UFC plans 45 fight cards this year: 13 pay-per-view shows and 32 televised Fight Night cards.
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