Fleshler's first major film was 1998's A Price Above Rubies. More recently, he has appeared in such films as Blue Jasmine, A Most Violent Year, God's Pocket, and The Rendezvous.
Fleshler's television credits include Billions, Sex and the City, Law & Order, Law & Order: Special Victims Unit, Fringe, Third Watch, Blue Bloods, Bored to Death, The Good Wife, and The Following. He portrayed George Remus in seasons 2–4 of Boardwalk Empire, and Errol Childress in Season 1 of HBO's True Detective. He played Dr. Cordell Doemling, Mason Verger's physician and henchman, in season 3 of NBC's Hannibal. He played Judge Roth in HBO's miniseries The Night Of.
