Sebastian's first small film role was given to him by film director Errol Williams, through the New Brunswick Filmmakers Co-operative in 1993. That first independent short film fueled his interest in going after more acting roles.

Since then Seabstian has held a variety of lead and principle roles in feature films, movies of the week, documentaries and television series. He has worked along side film personalities, such as William Hurt, Juliet Lewis, Daniel Baldwin, Megan Follows and Wendy Crewson.

Although Sebastian worked to develop a persona for himself around his bodybuilder physique initially, he has since found himself taking advantage of his ability to fit into a broad range of character types.