[6] After several years of television work under her belt, McCarthy secured a role in the made-for-television movie A Nest of Singing Birds (1987), receiving early recognition for her talent with a Gemini Award nomination for Best Performance by a Lead Actress in a Dramatic Program.

That year, she made her first notable impression on the Canadian movie scene as Polly, the quirky, "organizationally impaired girl" in Patricia Rozema's I've Heard the Mermaids Singing.

[4][5] She played Sarah Hamoudi in the Canadian television series Little Mosque on the Prairie (2007–2012), a role for which she was nominated for a Gemini award.

She is also an accomplished voice-over actress, having performed characters voices in Free Willy, Mythic Warriors: Guardians of the Legend, The Busy World of Richard Scarry, The Neverending Story, Bad Dog and Marvin the Tap-Dancing Horse.

[11] McCarthy is a spokesperson for The Quilt Project, a support group for families affected by breast cancer, and Canadian Feed the Children.