Irish middleweight John Duddy made it 19 wins in a row after beating American Anthony Bonsante in nine rounds.
The fight was stopped because of blood streaming from Bonsante's head following an accidental clash of heads in the second round.
In front of a sell-out 5,000 crowd in Madison Square Garden, the 27-year-old won a unanimous verdict and retained his IBA middleweight title.
It was the ninth defeat in 41 fights for the 36-year-old from Minnesota.
New York-based Duddy was already ranked in the top 10 by the WBA and WBO, helped by his victory last time out against veteran Yory Boy Campas last September.
Duddy proved too strong throughout against the former contestant of the US TV reality boxing series The Contender.
The Derry fighter acknowledged that he was "a little bit rusty" after being out of action for more than six months.
"At one stage, he was on his bike so much that I was thinking that he didn't want to fight any more"
"I was trying to land the big one. Instead, I should have let my punches do the work for me," said Duddy.
"Fair play to him. He was gutsy. He wanted to come here and survive. Unfortunately, it was stopped on a technicality but I think I won every round."
Duddy said that he believed that the clash of heads was accidental.
"It was the two of us. Anthony even apologised to me in the next (third) round and said 'sorry about the head'.
"From then on, he tried to keep moving and was very negative. I was trying to chase him down and at one stage, he was on his bike so much that I was thinking that he didn't want to fight any more."
Duddy thanked his fans for their "tremendous support" during the contest.
"Hopefully, it was a great occasion for them."
Such is Duddy's popularity, there was speculation after Friday night's win that his handlers may have to find a bigger venue than Madison Square Garden for any future bouts in New York.
Highlights of the Duddy-Bonsante bout will be shown on BBC One Northern Ireland on Sunday evening at 2220 GMT.