When Amy Beth Christenson's original concept art of Galen Marek looked strikingly like Sam Witwer, the vice president at the time noted the resemblance due to recognizing Witwer from Battlestar Galactica, so he was contacted to audition. From there, he became the complete basis for the main character's voice and appearance in Star Wars: The Force Unleashed. His likeness was created through motion capture for the game to build the character's appearance and range of facial expressions. Witwer's performance was recorded on HD cameras (as were all the actors who worked on the game). While the game was in production, Witwer only knew his character as "Starkiller." Witwer also voiced Galen Marek (known only as "The Apprentice") in Soulcalibur IV. Witwer returned to play Starkiller in the sequel Star Wars: The Force Unleashed II. For this character, he served in the same capacity as before by providing his voice and likeness to the main character. Witwer also voiced Palpatine in Star Wars: The Force Unleashed, and gave his voice and likeness to the imperfect genetic replicas and the Dark Apprentice in Star Wars: The Force Unleashed II.
He voiced Maul in the season 2 finale of Rebels, and a few episodes for the third season.
Witwer also provided additional voices in Rogue One: A Star Wars Story.
Witwer voiced the characters of Darth Maul and Emperor Palpatine in the game Star Wars Battlefront II.
Witwer provided the voice for Maul in Solo: A Star Wars Story.
Witwer provided additional voices in Star Wars Jedi: Fallen Order.
In addition to his work in Star Wars, he frequently competes in Star Wars trivia competitions.
- ""You're Hired" to be Darth Vader's Secret Apprentice!" – Star Wars Insider 97
- "Striking Back!" – Star Wars Insider 118
- "Back From the Depths!" – Star Wars Insider 132
- Star Wars in 100 Scenes
- "Zabrak Again!" – Star Wars Insider 168
- "Interview: Sam Witwer" – Star Wars Insider 199