Lucas made his feature film debut as an extra in Dan in Real Life, a film his father directed.
During a middle-school play, Lucas was spotted by the casting director for Wes Anderson's Moonlight Kingdom. He was later cast in the film as Redford.
He won critical acclaim for his role in Manchester by the Sea. That film earned him a Critics' Choice Movie Award for best young performer and a nomination for the Academy Award for best supporting actor.