The Victoria native finished with the third fastest qualifying time, touching in seven minutes, 49.58 seconds. Conor Jaeger of the United States posted the fastest time, followed by Sun Yang of China.
The 24-year-old Canadian will try and land on the podium for the first time in Barcelona, after settling for fourth in Sunday's 400 final.
Cochrane has twice previously won bronze at the world championships at the 800 distance, which does not appear on the Olympic programme. The final will take place Wednesday evening in Spain.
Cochrane took silver with a personal best in the 1,500 at last year's London Olympics, denied the victory by a jaw-dropping swim from Yang, who took more than three seconds off the previous world record. Cochrane also has an Olympic bronze, from the Beijing Games in the 1,500.
Barbara Jardin-Rojas of Notre-Dame-de-Grace, Que., managed to claim the last spot in the women's 200 freestyle final, which takes place later Tuesday, with Samantha Cheverton of Pointe-Claire, Que., not advancing.
American Missy Frankin, whose parents are from Nova Scotia posted the fifth-fastest time in the 200-meter freestyle at 1 minute, 56.90 seconds. Camille Muffat of France, a silver medallist in this event at last year's London Olympics, was top qualifier at 1:56.53.
Zach Chetrat of Oakville, Ont., was eliminated in the semifinals in the 200 butterfly, with Edmonton's Richard Funk failing to advance in the 50 breaststroke.
Tyler Clary led the field in the 200 butterfly, edging Olympic champion Chad le Clos of South Africa.
Cameron van der Burgh of South Africa topped the prelims for the 50 breaststroke, a non-Olympic event. Christian Sprenger of Australia, who beat van der Burgh for gold in the 100 breast, advanced in fourth.