The Jennifer's Body actress uploaded pictures of herself demonstrating various facial expressions in an apparent bid to silence speculation.
Fox named the photo gallery: "THINGS YOU CAN'T DO WITH YOUR FACE WHEN YOU HAVE BOTOX. (sic)"
The 25-year-old was recently named the fourth sexiest woman in the world by FHM, being replaced in the top spot by her Transformers successor Rosie Huntington-Whiteley.
Fox appeared in the first two Transformers movies alongside Shia LaBeouf, but departed the franchise last year. Huntington-Whiteley was then drafted in as the female love interest for the third outing, Dark of the Moon.
Fox previously spoke about cosmetic surgery in an interview with Allure, saying that people should really consider why they want to change their image before going ahead with any procedure.
"I would encourage anyone to first speak with a therapist, to try and figure out where this want comes from, because a lot of times it's not related to your teeth or your nose or your chin," she said. "The surgery is not going to alleviate that insecurity for you. If then you feel [like] this is something [you] want to do, then do it. It's amazing that we have the technology to do the stuff that we do."
Fox is currently working on Sacha Baron Cohen's new movie The Dictator, which revolves around "the heroic story of a dictator who risked his life to ensure that democracy would never come to the country he so lovingly oppressed".
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Watch the trailer for Passion Play, starring Megan Fox and Mickey Rourke, below: