Seater was born in Toronto, Ontario and began acting in the late 1990s. He appeared in the short films Night of the Living and The Stone Skipper, and had minor roles in the direct-to-video film Future Fear and the made-for-television films Rescuers: Stories of Courage: Two Couples, Vanished Without a Trace, On Thin Ice, Dirty Pictures, Cyber Seduction: His Secret Life, the Hanukkah-themed Jenny and the Queen of Light, as well as in episodes of several television series.

Seater voiced the title character in the series Mattimeo: A Tale of Redwall, which aired in 2000, starred as Lucas Randall in the television series Strange Days at Blake Holsey High, which began airing in 2002 and ended in 2006, and had a role in the 2005 film The Prize Winner of Defiance, Ohio, which starred Julianne Moore.

As of 2007, Seater appears in the recurring role of Owen on the series ReGenesis, which is in its third season, and plays Derek Venturi on another Canadian series, Life with Derek, which began in 2005 and as of September 2006, was in production on its third and fourth seasons. Seater has written a script for an episode of the show's fourth season with his brother, Graham.[1] He will join Degrassi's Stacy Farber in CBC's new series 18 to Life, in which they play 18-year-old newlyweds struggling to make their marriage work in spite of disapproving family and friends. In 2009 he played a character in the Degrassi movie Degrassi Goes Hollywood.

Seater attended the Etobicoke School of the Arts.

In 2009 he appeared as guest star in the second season of Murdoch Mysteries.