The Edgar Wright-directed movie is set for a 2015 release, and many comic book fans have tipped Fillion for the title role in the picture, reported Digital Spy.
However, the 42-year-old Firefly actor said, "I will not be playing Ant-Man. I'm pretty booked-up right now as far as work goes, and there's so much more going on in the entertainment industry than just, 'Oh, you know who would be great in that?' There's a lot more that comes into play."
Fillion, who currently plays the title role in 'Castle', also said that he feels as though he has been "fortunate" in his career.