After completing his education he went to work in a bank for five years, before he joined Radio Telifís Éireann as a newsreader/announcer. For two years he did interviews and presenting documentary features before moving to the Light Entertainment department as a disc jockey and host of TV quiz and variety shows. He first worked for BBC Radio presenting Midday Spin in the mid-1960s and, on the inauguration of BBC Radio 1 he presented Late Night Extra for two years, commuting weekly from Dublin to London. In April 1972 he took over the breakfast show on BBC Radio 2, where he has remained most of the time ever since, amassing an audience of up to six million. During this period he released his own version of "The Floral Dance", by popular request from listeners who enjoyed hearing him singing over the instrumental number one hit.
He has also presented many television programmes, including his thrice-weekly chat show Wogan for seven years, Come Dancing (a ballroom dance show), and the game shows Celebrity Squares, Blankety Blank, and his current show, Terry and Gaby (Roslin) on Channel 5. He is particularly famed for his sardonic commentaries on the Eurovision Song Contest which he has done annually since 1971.
In 1997 he was awarded an honorary OBE; as he is not a British subject he did not qualify for a full OBE.