Kate, who is pregnant with her third child, chose an elegant navy blue gown, detailed with black jewels, which accentuated her bump. The British actress swept her hair up into a chic bun and kept her accessories to a minimum, wearing only a simple silver bangle and glittering earrings.
"I feel completely great," said Kate to People magazine at the premiere. "It's such a pleasure to be able to be here and talk about a film that I'm proud to be a part of."
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The movie, Labor Day is based on a novel by Joyce Maynard and tells the story of troubled single mother Adele and her son Henry after they offer a injured man a lift in their car.
The film, which also stars Tobey Maguire, Josh Brolin and James Van Der Beek will hit cinemas at the end of the year.
Mum-to-be Kate arrived in the Canadian city on Thursday after being spotted making her way through Heathrow Airport walking hand-in-hand with her husband, Ned Rocknroll.
Oscar-winner Kate, 37, and Ned confirmed they were expecting their first baby together in June, with a spokesperson revealing that the new arrival is due at the end of the year.
While it will be Ned's first experience of fatherhood, his wife is already a mother to two children; Mia, 12, from her first marriage to Jim Threapleton, and son Joe, nine, from her second to Sam Mendes. The happy parents-to-be were married in December 2012 after a whirlwind romance.
Kate met Ned — who was born Ned Abel Smith before legally changing his name — while on holiday on Richard Branson's Necker Island.
Ned is the nephew of the Virgin mogul and works on the space travel branch of the Virgin empire, Virgin Galactic, with Princess Beatrice's boyfriend Dave Clark.