Robert Guerrero comfortably outpointed South Africa's Malcolm Klassen to capture the IBF super-featherweight title of Saturday.
The Californian boxer, who has also held the IBF title at featherweight, was never in trouble against the defending champion.
Guerrero, who knocked out the mouth piece of his opponent in the sixth round, did have to deal with a cut near his left eye after an accidental clash of heads.
Klassen, competing for the first time outside his native South Africa, lost out in his first defence of the belt he won only four months ago.
At the end of the fight, the judges' scorecards read 117-112, 116-112 and 115-113, all in favour of Guerrero.
Rant
In another fight on the card, held in the city of Houston, Texas, local fighter Juan Diaz secured a unanimous points victory over Paulie Malignaggi.
The New York native had already complained before the fight that he would fall victim to some home town bias from the judges and his loss proved controversial.
While two of the scores were relatively close, Gale Van Hoy gave the contest to Diaz by a large margin of 118-110.
After the defeat Malignaggi launched a stinging attack on the fight organisers and the sport in general.
"I had to deal with politics that was ridiculous. This state never gives a fair shake to someone fighting from Texas," he said.
"I get the short end of the stick. I am the loser so now I to go fight someone else in their home town."
