Desmarais began her career with a small roles in John Duigan's Head in the Clouds in 2004.
In 2010 she had a small role in Heartbeats directed by Xavier Dolan.
In 2013 she played the lead role in Sarah Prefers to Run which went on to play in the Un Certain Regard section at the 2013 Cannes Film Festival.
She was named a Rising Star at the 2014 Toronto International Film Festival.
She played the lead in the 2014 movie Hunting the Northern Godard.
