Cathal O'Shannon joined RTÉ’s “Newsbeat” in 1965. One of his best-remembered interviews is with Muhammad Ali (1972). Among his documentaries for television were 'Even the Olives are Bleeding' (1976), about Irish volunteers in the Spanish Civil War, and 'Emmet Dalton Remembers' (1978).
In 1978, he left RTÉ to join Canadian company Alcan, which was setting up an aluminium plant at Aughinish. He retired from Alcan in 1992 and returned to programme-making, including 'Murder in Ireland' and 'Ireland’s Hidden Nazis'. He won two Jacobs’ awards. In 2010, the Irish Film and Television Academy presented O’Shannon with a lifetime achievement award.