Director Josh Trank's superhero film was panned by critics and struggled at the box office, and now Kate admits she felt like she wasn't valued on the set.
"I had a horrible experience on 'Fantastic Four' and I've never talked about it before," she says in a new Television Academy interview. "Do I wish I had responded differently to certain things? Yes, definitely."
"The fact of the matter is that my two horrendous experiences with directors were male directors. Have I not gotten along with a female director? Absolutely. And was it not the greatest work experience? Sure. But there was never a time that I felt, 'This is happening because I'm a woman'."
"With the male directors, it 100 percent was only happening with me; it was a power dynamic thing. And on both of my bad experiences, the movies were 95 percent men and I was the only woman in the movie."
Kate also tells Collider, "I think that the thing that I always go back to on that one is that I think I should have followed my instincts more. Like when my gut was telling me, 'You probably shouldn't let that slide, what that person just said', or if you're feeling a certain way about what an energy is like and how that is affecting your performance... You're being paid to do a certain thing and if something is in the way of that, you have the right to speak up and say, 'I'm actually not able to do what I am here to do because of X, Y and Z'."
"I think that speaking up is something that I think that we all probably learn it over and over again, to follow your instincts and if you're feeling a certain thing that is uneasy or whatever, there's a reason for it. I regret not having stood up for myself. I regret that for sure."
But Mara insists she still doesn't regret making "Fantastic Four", because she met her future husband - Jamie Bell - on the set.
"I married one of my co-stars, so I don't regret doing that movie at all," she adds.