Page began acting at age 10, appearing in the telefilm Pit Pony, which would later spin-off a television series. This led to roles in a number of small Canadian films and television series. At 16, she was cast in an independent film shot in Europe, Mouth to Mouth.

Page played one of the main characters in the 2005 movie Hard Candy, and gained praise for "one of the most complex, disturbing and haunting performances of the year". As the title-character star of Juno, Page garnered substantial praise, including an Oscar nomination for the role. A. O. Scott of the New York Times noted her as being "frighteningly talented" and Roger Ebert said, "Has there been a better performance this year than Ellen Page's creation of Juno? I don't think so".

Page has roles in four films unreleased as of January 13, 2008: An American Crime, which premiered at the 2007 Sundance Film Festival; The Tracey Fragments, which is scheduled for a U.S. release in early 2008; The Stone Angel; and Smart People, which is scheduled to premiere at the 2008 Sundance Film Festival. She is also attached to star in Jack and Diane opposite Olivia Thirlby, with whom she co-starred in Juno.

In 2008, Page was nominated for an Academy Award for Best Actress for her performance in Juno.

Page was born and raised in Halifax, Nova Scotia, the daughter of Martha Philpotts, a teacher, and Dennis Page, a graphic designer. Ellen attended the Halifax Grammar School until grade 10, graduating from the Shambhala School in 2005.

As of January 2008, Page resides in her hometown of Halifax.