He began his professional boxing career on 10 May 1981, beating Selvin Bell by TKO in two rounds in Dublin. After another win, he suffered his first setback, losing a hotly disputed decision to Peter Eubank (brother of Chris Eubank) over eight rounds at Corn Exchange at the Brighton Dome. After his first loss, McGuigan notched up two more wins, including one over Terry Pizzarro, and then he was given a rematch with Eubank. The second time around, McGuigan prevailed, by a knockout in the eighth round.