Alison learned to play the drums for her role as Kim Pine and surprised both herself and her cast mates by quickly learning the difficult instrument. She sings and plays drums in the film as well as on the soundtrack. Her acting performance as Kim Pine is characterized by the fact that she almost never blinks or breaks eye contact through the course of the film.
Pill was born in Toronto, Ontario, Canada. Her father, a financier, is Estonian. Alison attended Vaughan Road Academy. In 2006, she starred as Grace Webster in the short-lived NBC drama The Book of Daniel, and was nominated for a Tony Award for her performance in Martin McDonagh's The Lieutenant of Inishmore. Pill had a major supporting role as campaign manager Anne Kronenberg in the Oscar-winning 2008 film Milk.
Shortly before the Scott Pilgrim movie she starred as April, a college student who discovers she has cancer, in the HBO series In Treatment.
Pill was previously engaged to actor Jay Baruchel. Baruchel made their engagement public when he thanked his fiancée (Pill) during an acceptance speech at the Genie Awards in Ottawa, Canada. The two have now split up.