Born in the remote northern logging town of Greenville, California and raised in Modesto, California, Marsters always knew he wanted to be an actor. From his debut as Eyeore in a fourth grade production of Winnie the Pooh, he went on to study acting at New York's prestigious Juilliard. He began his professional career in the theater, performing in stage productions including The Tempest and Red Noses at Chicago's renowned Goodman Theatre. In addition, Marsters revisited the stage in Los Angeles with a starring role in an original play produced by Noah Wyle titled The Why.

Marsters made his onscreen debut guest-starring on the television series Northern Exposure. He landed the prominent role of an ill-at-ease priest, which was cast locally in Seattle, soon after moving to the Pacific Northwest. He was inspired by the success to move to Los Angeles and within months was sinking his proverbial teeth into the role of Spike on Buffy the Vampire Slayer. Marsters, no stranger to television, starred in the anthology series Strange Frequency for VH1, as well as in Gene Roddenberry's Andromeda.

Other credits include the feature The House on Haunted Hill, a psychological horror film that also starred Geoffrey Rush, Famke Janssen, Taye Diggs and Lisa Loeb.

Marsters toured Europe with his band, Ghost of the Robot, to promote their new CD, Mad Brilliant. The band sold out all of their engagements in London and Germany and they continue to play to sold-out audiences in Los Angeles.