Byrne's first major role came in the final season of the Irish television show The Riordans. From there he went on to star in a spin-off series Bracken. His movie debut did not come until 1981, when he appeared in Excalibur, as Lord Uther.

Currently, Byrne can be seen in In Treatment and next in King of the Pipers and The Snow Prince. He won an Golden Globe for her performance in In Treatment. Byrne can also be seen in Camelot, with the New York Philharmonic, from May 7th through the 10th of 2008. Camelot marks his return to the theatre.

1. "I'm not a very gregarious person. I can't bear attention being called to me in a public place, which is ridiculous in a business that pays you to be noticed." — Gabriel Byrne on himself
2. "Guilt is the most meaningless of emotions. It means nothing. As Barbra Streisand says, 'I got nothing to be guilty of...." — Gabriel Byrne on guilt
3. "How the hell can you compare one actor to another? It's ridiculous. You just can't." — Gabriel Byrne on comparing actors
4. "A completely disrespectful photographer was asked to stop taking photographs, and then said, 'I've got what I want. What are you going to do about it?' How would you feel if somebody walked up and started taking your photograph? I don't think you'd be very happy." — Gabriel Byrne on an encounter with a photographer