In 1945 Walsh moved to Britain and briefly joined the Croydon Repertory. Upon his return to Dublin he was spotted by a talent scout from the Rank Organisation. This led to parts in Bedelia, Hungry Hill and The Mark of Cain, and the beginning of Walsh's career in film. He appeared in seven films as a leading man, before returning to the theatre. Walsh later resumed his film career in a series of B movies. He appeared in over forty films made for film and a hundred for television, making his final film appearance in 1983.