A Juilliard graduate, Kline made his Broadway debut playing Vershinin in Anton Chekov's The Three Sisters for John Houseman's The Acting Company, of which he is a founding member. His other Broadway credits include Hal Prince's On the Twentieth Century, for which he won both a Tony and a Drama Desk Award, and The Pirates of Penzance, for which he again won both a Tony and a Drama Desk Award, as well as the Obie Award for Outstanding Achievement by an actor. After his film debut in Alan Pakula's adaptation of William Styron's novel Sophie's Choice, Kline began a long-standing creative relationship with writer/director Lawrence Kasdan. Their collaborations included the influential ensemble comedy The Big Chill, followed by the Western Silverado, the offbeat comedy I Love You To Death, the ensemble drama Grand Canyon and the romantic comedy French Kiss. Kline's other film credits include Lord Richard Attenborough's Cry Freedom, Ang Lee's The Ice Storm, and Michael Hoffman's Soapdish, A Midsummer Night's Dream and The Emperor's Club.
Kline's other Broadway performances include Shaw's Arms and the Man directed by John Malkovich, and Gerry Gutierrez's production of Chekov's Ivanov at Lincoln Center. His roles at the New York Shakespeare Festival have included Richard in Richard III, Henry in Henry V, Duke Vincentio in Measure for Measure, Benedick in Much Ado About Nothing and the title role in Hamlet, for which he won the Obie Award for Sustained Achievement in Theatre. He directed and starred in a second production of Hamlet, which received five Drama Desk nominations, including best director and actor nominations for Kline. Later, he co-directed a televised version of the production for the PBS Great Performances Series. Kline appeared opposite Meryl Streep in Mike Nichols' critically acclaimed production of Chekhov's The Seagull, for the Public Theater's "Shakespeare in the Park." He recently won a Drama Desk award for his performance as Falstaff in Lincoln Center Theater's production of Henry IV, directed by Jack O'Brien. He will be seen in Bertolt Brecht's Mother Courage and Her Children at the Delacorte Theater in New York City during the Summer 2007. Kline is the first American actor to receive the Sir John Gielgud Golden Quill Award, and he was recently inducted into the Theater Hall of Fame. He will soon be seen in the romantic comedy Definitely, Maybe and as the voice of "Andre" in the animated The Tale of Despereaux.