Irishman TJ Doheny was beaten on points by WBA super-bantamweight champion Daniel Roman in their unification bout in Los Angeles.
Doheny, who held the IBF belt, was knocked down twice at The Forum as he suffered the first defeat of his career.
Two judges scored the fight 116-110 in favour of 28-year-old Roman and one scored it a draw.
Doheny, 32, had won his previous 21 fights, with 15 knockouts.
Victory was a 19th in succession for Roman, who now has a career record of 27 wins and two defeats from 30 bouts.
Doheny emigrated to Sydney 10 years ago and has never fought as a professional in Ireland.