A two-time Gemini winner, recent Genie winner, and multiple Gemini and Genie nominee, Sarah has been in front of audiences since the age of four. The last of eight children, she is the daughter of actor Michael and the late Diane Polley. It was she who wanted to get into acting in the first place, although her parents were against it at first.

During her childhood, before portraying Avonlea's "story girl"--Sara Stanley--she held the title role in the PBS series Ramona (which earned her her first Gemini nomination in 1988) and held roles in movies like Prettykill, One Magic Christmas, and The Adventures of Baron Munchausen, as well as guest-starring in other series like Friday the 13th: The Series. In Avonlea's first year, she received her first Gemini for her role as street waif Jody in Sullivan's adaptation of Lantern Hill. She stayed on Avonlea until the end of the fifth season (although she initially wanted out after the second season; her role as Sara Stanley, Avonlea's "story girl" earned her three Gemini nominations). As she left the series, she took on a small role in Atom Egoyan's Exotica and later wowed Stratford Festival audiences with her performance in their production of Alice Through the Looking Glass.

Sarah wanted to do more, though. She took some time away from acting and got into activism, allying herself with Canada's New Democratic Party (NDP) and, eventually, the Ontario Coalition Against Poverty (OCAP). During a 1995 protest, she got two of her teeth knocked in and had a third loosened by a police baton. She continued to be involved in activism full-time for a little longer, but then returned to acting soon after. In 1996, she was in the movie Joe's So Mean to Josephine; but it wasn't until a year later that she came into her own as an adult actress, when she starred as Nicole in Egoyan's film The Sweet Hereafter, based on the novel by Russell Banks. Her performance earned her rave reviews worldwide, as well as two Genie nominations--one for Performance by an Actress in a Leading Role, and another for Best Original Song, for singing the title track (she contributed her voice to four other songs on the movie's soundtrack).

In 1998, she received three Gemini nominations--one for a small role in Clement Virgo's The Planet of Junior Brown, one for her riveting performance in White Lies, and another for her guest appearance as goth girl Lily in the short-lived TV series Straight Up (which turned into her second Gemini win). More recently, she appeared in movies such as Go, Guinevere, eXistenZ, Last Night, The Life Before This, The Claim, and The Law of Enclosures, which earned her her third Genie nomination.

Sarah also has an affinity for working behind the camera as well, having written and directed three short films--Don't Think Twice, The Best Day of My Life, and I Shout Love--for which she won her first Genie in 2003. Upon that win, she told a member of the press that she'd begun work on what she believes will become her first feature film as a writer/director. In March 2004, she appeared as a nurse in a remake of Dawn of the Dead. That same year, she won her first Genie for her acting work, taking home the prize for Best Actress in a Leading Role for her role in My Life Without Me. More recent projects include The Event, Luck, Siblings, Sugar, and Don't Come Knocking (which screened at the 2005 Cannes Film Festival).

She continues to be involved in activism (in the summer of 2001 she helped organise a hospital benefit), and she also plays the flute. In the late summer of 2003, Sarah married her long-time boyfriend, film editor David Wharnsby.