Vaulted to fame at a young age with her starring roles in Kick-Ass, Hugo, and Let Me In. She then went on to play Carrie in the 2013 remake of the film, Angie Steadman in 2010's Diary of a Wimpy Kid, and Mia Hall in 2014's If I Stay. She landed the role of Cassie Sullivan in the 2016 action film The 5th Wave.
She had her first major big-screen acting role in 2005 in the remake of The Amityville Horror.
She provided the voice of Darby on the television show My Friends Tigger & Pooh.
She was raised in a Christian family with four older brothers. Her parents, Teri and McCoy Moretz, divorced when she was growing up. She was in an on-and-off relationship with Brooklyn Beckham for multiple years.