The 33 year-old improved to 25-0 with what was a strange ending to his contest with contender-turned journeyman Fulgencio Zuniga.
Eight rounds of solid action that Monaghan had the better of came to a head in the next round, although it was Zuniga who landed the final blow.
The Colombian landed a cracking overhand right to the jaw of Monaghan but failed to get back up when bundled to the floor by the New Yorker.
Zuniga, who was told to get up by the official, decided instead to take a knee and the fight was then waved off with the former IBO champion in no position to continue.
More results to follow…