11 October 2016 Last updated at 08:05 BST
She revealed to Newsround that coaches she met didn't think she'd be able to box - but that she proved them all wrong.
Nicola won boxing gold at London 2012 and Rio 2016.
The smiley star spoke to Newsround for Women's Sport Week, a campaign to encourage more girls to get involved with sport.
Olympic champion boxer Nicola Adams says she was told that "women can't box" when she started her career.