He appeared in the 2004 feature film Envy as the son of Ben Stiller and Rachel Weisz's characters, and played the son of Wendy Malick and Sam Robards' characters in the pilot for an ABC sitcom entitled My Life With Men (2003), and the son of John Leguizamo and Claire Forlani's characters in an untitled Brett Ratner-directed pilot for CBS.
Lerner voiced one of the leads, Chowder, in the computer-animated film Monster House (2006). He was nominated for the 2006 Annie Award for Best Voice Acting in an Animated Feature for his role, and was beaten for the award by Sir Ian McKellen.
He has appeared on the television shows Malcolm in the Middle, The King of Queens, Two and a Half Men, Oliver Beene, and Sonny With a Chance, and had a recurring voice role on the Cartoon Network show Whatever Happened to Robot Jones?. He did voice work for Zak Saturday, a character from the Cartoon Network show The Secret Saturdays.
On October 16, 2017, Lerner was cast in the Blumhouse supernatural thriller film Truth or Dare. The film was released in theaters on April 13, 2018.
Lerner was born in Riverside, California, the son of Patti (née Klein), a reporter, and Ken Lerner, an actor. His uncle is actor Michael Lerner, and his family is of Jewish descent. Since 2018, he is in a relationship with Smosh member Olivia Sui.