The actress's alter ego Alisha was killed off in Sunday night's (December 18) third series finale.
Writing on her official Twitter page, Thomas said: "I wont (sic) be coming back for series 4 but I can't wait to see it! I've had an amazing time in misfits- it has been epic!xxx"
She later thanked fans for their "lovely comments" on the social networking site.
Thomas told Digital Spy earlier this year that she thought seeing a rumoured American remake would be "very interesting", particularly given that the show is "a British take on... the American superhero [genre]".
Gossip Girl creator Josh Schwartz is planning a remake, working in collaboration with UK Misfits creator Howard Overman.
> 'Misfits' renewed for fourth series
> 'Misfits': The season finale in pictures
Watch Antonia Thomas and Iwan Rheon, who plays Simon, talking to Digital Spy below: