Ezra Matthew Miller was born in Wyckoff, New Jersey, to Marta (Koch), a modern dancer, and Robert S. Miller, who has worked at Workman Publishing and as former senior V.P. for Hyperion Books. Ezra has two older sisters and is of Ashkenazi Jewish (father) and German-Dutch (mother) ancestry; Ezra has described themselves as Jewish and "spiritual".
As a child, Miller sang with the Metropolitan Opera and attended Rockland Country Day School and The Hudson School. Their first feature film was the independent Afterschool (2008), and Miller subsequently appeared on the television series Californication (2007), Law & Order: Special Victims Unit (1999), and Royal Pains (2009), and in the films City Island (2009), Every Day (2010), Beware the Gonzo (2010), and Another Happy Day (2011).
Miller drew critical praise playing Kevin Khatchadourian, the homicidal son of Tilda Swinton's character, in the dramatic thriller We Need to Talk About Kevin (2011). They subsequently played Patrick in the well-received teen drama The Perks of Being a Wallflower (2012), opposite Logan Lerman and Emma Watson.
Ezra's other roles include the period piece Madame Bovary (2014), Judd Apatow's comedy Trainwreck (2015), and the psychological thriller The Stanford Prison Experiment (2015). They have been cast as superhero The Flash in The Flash (2023), scheduled for release in 2022.