Kenneth Lonergan grew up in New York City and has lived there his entire life. He attended the Walden School in Manhattan and graduated from New York University. He began writing plays in high school and at age eighteen saw his play The Rennings Children produced by the Young Playwrights Festival in 1982. After graduating from college, he was affiliated with Naked Angels, an Off-Broadway troupe, while also working as a speechwriter and corporate scriptwriter.
Lonergan’s father was a doctor and his mother a psychiatrist; after they divorced, his mother married another psychiatrist. Lonergan has a brother, half-brother, and several stepsiblings, and relationships among siblings are an important theme in his work. He also drew on personal experience in writing The Waverly Gallery, based on his observations of his grandmother’s struggle with Alzheimer’s disease.
The stage success of This Is Our Youth led Lonergan to Hollywood to work on a variety of projects, including the box-office and critical failure The Adventures of Rocky and Bullwinkle. Although unhappy with the process of writing screenplays under studio control, Lonergan did not abandon screenwriting but instead sought independent production for You Can Count on Me. The play Lobby Hero, though produced after the film success in 2001, was written and contracted for production in 1998. In 2000, Lonergan married J. Smith-Cameron, an actress who appears in You Can Count on Me.