The 22-year-old actress - who recently gave her first interview since admitting to cheating on Robert Pattinson - looked demure in a sheer couture dress embroidered with flowers by Zuhair Murad.
The young starlet teamed the frock with a pair of simple black Jimmy Choo courts and wore her hair swept back over her shoulder.
Stewart was joined at the screening by co-stars Kirsten Dunst, looking equally as elegant in an ivory Christian Dior gown, Garrett Hedlund, who is currently dating Dunst, and director Walter Salles.
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The film's fellow stars Tom Sturridge - who is said to be the best friend of Pattinson - and Sam Riley were absent from the premiere.
Photo gallery - Toronto On the Road premiere: