Has been a member of Ensemble Studio Theater for thirty-some years. He has acted there in Lenin's Embalmers and Pigeon, both directed by William Carden, and in many other plays. He has directed plays on the EST stage, including plays by Shirley Lauro, David Mamet and Murray Schisgal, most recently Schisgal's Existence, with Kristin Griffith and Richmond Hoxie. He was inspired by the very first EST Marathon of short plays to write Bicycle Boys, which was produced in that seminal event and revived in the show Three From Ensemble Studio Theatre. Other plays by Maloney produced by EST include Lost and Found, Last Chance Texaco, Pastoral, Bad Blood (Salamander) and In The Devil's Bathtub. His play Accident was produced in Marathon 2000 and published in the anthology by that name published by Faber and Faber. In The Devil's Bathtub was published in the Kenyon Review. Other "autobiographical fictions" produced in one form or another at EST include My Father's Funeral, Accordion Dreams and Kolossal Hero

As an actor Mr. Maloney was most recently seen in the Atlantic Theater's production Dying For It. He has appeared in twenty-two plays at the Atlantic, where he is a member, including John Guare's Three Kinds of Exile, Lucy Thurber's Bottom of the World and Family; David Auburn's adaptation of The New York Idea; Peter Parnell's Trumpery; David Mamet's The Voysey Inheritance and many others. At the Irish Repertory Theatre he has appeared in Ernest in Love, It's a Wonderful Life and Port Authority, for which he was honored as Best Actor of the Year by Origin's First Irish 2014. He played "God Who Judges" in Ethan Coen's Almost An Evening at the Atlantic and starred with Estelle Parson's in David Hare's The Bay at Nice at Hartford Stage.

He was nominated for a Drama Desk Award and won the Richard Seff Award for his performance in John Patrick Shanley's Outside Mullingar on Broadway. Other Broadway appearances include West Side Story; Judgement at Nuremberg, with Maximillian Schell; Poor Murderer, with Maria Schell; Hughie, with Ben Gazzara; Tom Stoppard's Arcadia, with Billy Crudup; John Guare's Six Degrees of Separation; Our Town; Dinner at Eight; Carousel; and Abe Lincoln in Illinois (Lincoln Center Theater). For four years he was a member of Joseph Chaikin's Open Theater, appearing here and in Europe in The Serpent, Terminal, Ubu Cocu and Endgame, playing "Clov" to Chaikin's "Hamm." 

He has appeared in over fifty films, including Boiler Room, Requiem for a Dream, JFK, Washington Square, K-Pax, A Little Romance (with Laurence Olivier), and John Carpenter's The Thing! He has been seen on television in Stephen Soderbergh's "The Knick"; "Gotham"; "Black Box"; Alex Haley's "Queen"; Garson Kanin's "Moviola"; "East of Eden"; all the "Law & Order" franchises and as "Uncle Red" on "Rescue Me."

Maloney directed Sandra Bullock in Larry Ketron's No Time Flat; Kevin Bacon in the American Premiere of John Byrne's The Slab Boys; Tommy Lee Jones in Jack Gilhooley's The Time Trial; Adolph Green and Phyllis Newman in Murray Schisgal's The New Yorkers (which started at EST as Pushcart Peddlers); and Lois Smith and Thomas Gibson in Romulus Linney's Juliet, also at EST.

For several years Mr. Maloney was a critic for the magazine Changes, writing essays on theater and the arts. His memoir of acting in O'Neill's Hughie "Who Does Little But Listen," was recently published in the Eugene O'Neill Review. His adaptation of Machiavelli's Mandragola was commissioned by Washington D.C.'s Shakespeare Theatre, produced there under his direction and published by Broadway Play Publishing. His latest play Abu Ghraib Triptych, was first produced by Signal & Noise Theater in New Hampshire, then by the Alley Theater in Toronto. The first production was called "a shocking dramatic success as well as a rare example of art confronting our present national dilemma." Two parts of Abu Ghraib Triptych, Leash and Witness, have been published in the series Best American Short Plays, and Leash was also published by Joyce Carol Oates in her Ontario Review.

Mr. Maloney is a member of the Actors Studio, an alumnus of the New Dramatists and was a Fox Foundation Fellow in the year 2000.