When Bettany was nineteen, he decided to be an actor, and he pursued that career with determination, studying at the London Drama Centre in Chalk Farm. He made his stage debut in Stephen Daldry's acclaimed West End revival of An Inspector Calls at the Aldwych Theatre, playing the part of Eric Birling. He also appeared in the Royal Shakespeare Company's productions of Richard III, Romeo and Juliet, and Julius Caesar (for which he received a Charleson Award nomination). When Bettany was 21 he appeared in a BBC production of Oliver as Bill Sykes.

After appearing in the finale of Sean Bean's series Sharpe as HRH The Prince of Orange at the Battle of Waterloo, he made his film debut with a small part in Bent, a Holocaust drama which also featured Clive Owen, Jude Law, and Ian McKellen. He continued doing work in stage and television, these included Joe Penhall's Love and Understanding, which played at London's Flatbush Theatre and then ran in Connecticut. His roles in the televisio