John Fergus Slattery was born in Dun Laoghaire on 12 February 1949 and educated at Blackrock College and University College, Dublin. He was employed as an auctioneer and property consultant. Between 1970 and 1984 he played 61 internationals for Ireland as an open-side flanker and captained his country on 17 occasions. He toured Australasia in 1971 and South Africa in 1974 with the British Isles, making 25 appearances, including four tests against the Springboks. Fergus Slattery's 18 appearances for the Barbarians included a try-scoring contribution in the victory over New Zealand in 1973. He captained the Barbarians against Moseley (1974), East Midlands (1979 and 1980) and Scotland (1983).