Child actor known for his leading roles in the 2017 films It and The Book of Henry. He has also landed roles in notable films that include St. Vincent, Midnight Special, The Confirmation, Aloha and Knives Out. He also starred in season three of Masters of Sex.
He and his family moved to Los Angeles in 2011 without him knowing that acting would be in his future. He starred in commercials to break into acting.
His role in St. Vincent earned him a Las Vegas Film Critics Society Sierra Award for Best Youth in Film and a Phoenix Film Critics Society Award for Best Performance by a Youth in a Lead or Supporting Role. In 2018, he changed his last name from Lieberher to Martell.
He worked alongside Bill Murray in St. Vincent and Aloha.