Sarah Gadon first appeared in the episode Episode: "Last Night" of the Canadian action-drama television series ‘La Femme Nikita’ in 1998. She went on to appear in television series and films such as ‘Are You Afraid of the Dark?’ (1999), ‘Twice in a Lifetime’ (2000), ‘The Other Me’ (2000), ‘In a Heartbeat’ (2000), ‘Mattimeo: A Tale of Redwall’ (2000), and ‘Mutant X’ (2000). Gadon made her big-screen debut in the 2003 romance comedy-drama film ‘Fast Food High’ directed by Nisha Ganatra. The following year, she starred as ‘Margaret’ in the comedy film ‘Siblings’ directed by David Weaver. The film received a mixed response from critics. In 2005, she joined the voice cast of the animated television series ‘Time Warp Trio.’ She voiced the character ‘Jodie’ and remained a part of the show till 14 episodes. Gadon continued to appear in voice roles in television series like ‘Ruby Gloom’ (2006-2007), ‘Friends and Heroes’ (2007-2009), and ‘Total Drama’ (2007-2011).
In 2007, she was seen playing the role of ‘Priscilla’ in the American comedy-drama film ‘Charlie Bartlett’ directed by Jon Poll. Despite opening to mixed reviews, the film tanked at the box office. In 2008, she appeared in the Episode: "Attention Shoppers" of the Canadian crime drama television series ‘Flashpoint.’ While she only starred in a single episode of the show, her performance earned her the ‘ACTRA Award’ and ‘Gemini Award’ nominations. That same year, she became a part of the Canadian drama series ‘The Border.’ She played the role of ‘Zoe Kessler’ and remained a part of the show until 2009. Gadon continued to appear in television series like ‘Aaron Stone’ (2009), ‘Being Erica’ (2009), ‘Murdoch Mysteries’ (2009-2011), ‘Happy Town’ (2010), and ‘The Dating Guy’ (2010). In 2012, she starred as ‘Elise Shifrin’ in the Canadian drama-thriller film ‘Cosmopolis’ directed by David Cronenberg. The film received a positive response from critics. Gadon also received the ‘Vancouver Film Critics Circle Award’ for her role. She was next seen playing the role of ‘Helen St. Claire’ in the Canadian psychological drama film, ‘Enemy.’ The film won 5 Enemy ‘Canadian Screen Awards’ including the ‘Canadian Screen Award’ for ‘Best Supporting Actress’ for Gadon.
She next starred in films like ‘The Nut Job’ (2014), ‘The Amazing Spider-Man 2’ (2014), ‘The Girl King’ (2015), ‘A Royal Night Out’ (2015), ‘Indignation’ (2016), ‘The Death & Life of John F. Donovan’ (2018), ‘The Great Darkened Days’ (2018), ‘American Woman’ (2019), and ‘Vampires vs. the Bronx’ (2020). Gadon was last seen in the 2021 Canadian drama film ‘All My Puny Sorrows’ directed by Michael McGowan. She is all set to appear in the upcoming American black comedy film ‘Corner Office.’