Cochrane, racing in the men's 200-metre freestyle, was in seventh place at the halfway point before emerging with the two fastest final splits to win the race in 1:49.04 seconds.
Alec Page of Victoria took the silver in 1:49.33 and Coleman Allen of Vancouver was third in 1:49.40.
"This is why we train every day," said Cochrane, whose main focus is the 400 freestyle and 1,500 freestyle later this week. "It was great to be in such an exciting race. I'm glad I had some good back end speed."
The four-day trials serve as the selection meet for this summer's Commonwealth Games in Scotland, and the Pan Pacific swimming championships in Australia. Up to three swimmers can qualify in each event.
In women's events, Vancouver's Tera Van Beilen clocked the fastest time in the 200 breaststroke, beating out three other women who all swam under the qualifying standard.
Van Beilen, a 2012 Olympian, led from the beginning and held on in a tight finish in 2:26.66, 1.46 seconds less than the qualifying standard time.
Kierra Smith of Kelowna, B.C. was second at 2:26.74, and Toronto's Martha McCabe overcame her clavicle injury to finish third at 2:27.03.
"I finally got the better side of the touch, which doesn't happen too often for me," said Van Beilen. "I knew from this morning's preliminaries that it would be close. I tried to gauge the race situation as best I could."
Ashley McGregor of Pointe-Claire, Que., was fourth at 2:27.11.
Sinead Russell of Simcoe, Ont., highlighted the fastest time for the women's 100 backstroke, clocking one minute flat.
The top three racers in the women's 100 backstroke final went under the 1:01.25 standard. Brooklyn Snodgrass of Calgary was second in 1:00.23, while world championship 200 medallist Hilary Caldwell of White Rock, B.C., was third in 1:00.99.
"I'll take that for now," said Russell, the Canadian record holder. "It was a pretty good race. I'm looking forward to seeing what I can do later this season."
In the women's 200 freestyle, Brittany MacLean of Toronto took the national title clocking a personal best 1:57.57 with Samantha Cheverton of Pointe-Claire, Que., second in 1:59.28 and Alyson Ackman, also of Pointe-Claire, third at 1:59.60. MacLean's time was under the individual qualifying standard.
"I'm excited with my swimming," said MacLean. "I wanted to get this meet off to a really good start and keep building from there."
Emily Overholt of West Vancouver, B.C., and Barbara Jardin of Montreal tied for fourth at 1:59.88.
Other winners in men's competition were Russell Wood of Calgary, who beat the qualifying standard in the 100 backstroke by 0.01 seconds and Richard Funk of Edmonton in the 200 breaststroke.
The teams for the Commonwealth and Pan Pacific Championships will be announced Saturday night after the final races.