Born and raised in New York City, she made her acting debut opposite Robert De Niro in Martin Scorsese's Raging Bull, for which she received nominations for the Academy Award for Best Supporting Actress, the Golden Globe Award for Best Supporting Actress – Motion Picture, and the British Academy Film Award.
Her film appearances include Neighbors, White of the Eye, Kindergarten Cop, Soapdish, Matinee, Casper, Cop Land, But I’m a Cheerleader, Analyze That, The Bounty Hunter, The Double, and Patti Cake$.
Moriarty has also starred in numerous television series including Tales from the Crypt, Hey Arnold! , Law & Order, Law & Order: Special Victims Unit, Law & Order: Criminal Intent, I'm Dying Up Here, This Is Us, The Assassination of Gianni Versace: American Crime Story, City on a Hill, and HouseBroken to name just a few.
Moriarty works as an activist for the Autistic community and is the national spokesperson for Autism United.