Police and paramedics responded to a call that came in at 5 p.m. Tuesday regarding a stabbing on Rogerson Road, near Mavis Road and Matheson Boulevard West.
A man in his 50s was rushed to hospital, but succumbed to his injuries.
Police say they cannot identify the victim or the accused due to the provisions of the Youth Criminal Justice Act.
The accused teenager faces a charge of second-degree murder. She was due to appear in court on Wednesday for a bail hearing.
Anyone with information is asked to contact homicide investigators at 905-453-2121, ext. 3205, or to call Peel Crime Stoppers at 1-800-222-8477.