He is, among other roles, known for playing Chief Engineer Olson in Star Trek (2009), Theodore Groves in Disney's Pirates of the Caribbean (2003, 2007-2011), and Trevor Wilcox in Touch (2013), as well as voice roles such as Anders in Dragon Age: Origins – Awakening (2010), Cullen in multiple Dragon Age games, and Jet-Vac in the Skylanders video game series, as well as in the series Skylanders Academy.
In film, Ellis is known for appearing alongside Leonardo DiCaprio and Kate Winslet in Titanic as well as Brad Pitt and Angelina Jolie in Mr. and Mrs. Smith.
He was also a regular on the Fox drama Touch as Trevor Wilcox and played the villainous Michael Amador opposite Kiefer Sutherland in the 3rd season of the hit series 24.
His other television credits include: Dexter, The X-Files, Magnum PI, The Riches, Bones, Alcatraz, Star Trek: Deep Space Nine, The Closer, CSI, Nip/Tuck, Perception, Knight Rider, Days of Our Lives, Trust Me, and many more.
He reprised his role as Cait Sith in the English version of the CGI film Final Fantasy VII: Advent Children.
He has also been charged with several misdemeanors, including perjury, making a false written statement, three counts of coercion, aggravated harassment, and unlawful dissemination or publication of an intimate image, commonly referred to as “revenge porn,” under New York state law.