The 28-year-old beauty rose to fame on 'That 70's Show' at the age of 14 and has since starred in movies including "Black Swan" and "Forgetting Sarah Marshall".
But Kunis said that she has never been too sure she is any good in Hollywood, reported Contactmusic.
"I always assume that people underestimate me. Why not? Why wouldn't they? I have everything working against me at this point. I am a woman, I'm a child actress and I was on a television show for eight years. But I have worked really hard to prove them all wrong," Kunis said.
"It's the stubborn side of me, I still don't have a clue what I'm doing. I'm confident in my talent, whatever that may be, and I hope I never am. Working this hard is the thing that keeps me sane," she added.
R&B star Rihanna and rapper Drake are leading the MTV Video Music Awards (VMA) nominations with five nods each.