Kieran can currently be seen in his critically acclaimed performance as Roman Roy in the HBO series SUCCESSION, produced by Adam McKay and Will Ferrell for which he has received two consecutive Golden Globe nominations. Prior to that, Kieran starred in Noah Hawley's Emmy and Golden Globe-winning FX series FARGO.
On the feature film front, Kieran starred in the feature IGBY GOES DOWN, for which he received a Critic’s Choice Award and a Golden Globe nomination. He has also appeared in Edgar Wright’s SCOTT PILGRIM vs. THE WORLD, Todd Solondz’s independent film WIENER-DOG opposite Julie Delpy, Greta Gerwig, and Danny DeVito, Kenneth Lonergan’s MARGARET opposite Anna Paquin.
Other notable film credits include INFINITY BABY opposite Martin Star and Nick Offerman, THE MIGHTY, THE DANGEROUS LIVES OF ALTAR BOYS, THE CIDER HOUSE RULES, MUSIC OF THE HEART, PAPER MAN, and MOVIE 43.
On Broadway, Kieran starred in Kenneth Lonergan’s THIS IS OUR YOUTH opposite Michael Cera and Tavi Gevinson.