John O'Callaghan has performed in Canada, Ireland and the USA. He left home at 17 to study Computer Science at the University of Ulster in Belfast. He started to act at the same time with Belfast Youth and Community Theatre - with a mandate to bring protestant and catholic actors together. The New Theatre school followed in Boston, Massachusetts. Theatre school graduation followed and he decided to pursue his craft in Toronto, Canada. He quickly became a member of Canadian Actors Equity and a working actor. His first equity show was Carolan's Farewell at the prestigious DuMaurier Theatre Centre.

With an impressive resume he moved to New York City to star in the one man show Rum and Vodka written by Conor Mcpherson. This was a huge success. He went on to perform the show for NBC and HBO. Selling the show out night after night. Other New York credits include The Comedians at La Mama etc. and The Hostage at the Irish Repertory Theatre. After several Regional (including The Cleveland Playhouse) and other New York successes he moved to Los Angeles where he now resides with his son Odin and dog Charlie.

John was last seen in New York City starring in Howie the Rookie by Mark O'Rowe at the Irish Arts Centre, directed by the Emmy Award Winner Nancy Malone and playing Stephen Dedalus in Bloomsday on Broadway.

Premieres include Marina Carr's By the Bog of Cats, Conor Mcpherson's Rum and Vodka, playing Godzilla in Yasuhio Ohashi Godzilla (Crow's Theatre), Mark O'Rowes Howie The Rookie and The Live Full Monty at the New Yorker Theatre.

He performs regularly with California's Artists Radio Theatre and LA Shorts at the Getty.

Film and TV credits include We Were The Mulvaney's, The Agency, Clutch, Deep In My Heart, Haven't We Met Before and Gangs of New York.

He most recently completed the mini series ZOS Zone of Separation.