Sakio Bika won the vacant WBC super-middleweight title after beating Marco Antonio Periban via a majority decision at Barclays Center in New York.
The Cameroon-born Australian fighter had failed on three previous attempts to win world titles but finally managed to take a super-middleweight crown.
He was given the fight by scores of 116-112 and 115-113 on two of the judges' scorecards, while the third scored it even at 114-114.
"It means a lot. Periban was a very tough guy. I respect him. Like all Mexicans, he comes to fight," Bika said after the bout.
Periban brought a perfect record of 20-0 into the contest but a late flurry could not stop him from suffering the first defeat of his career.
"I won this fight, and the people in the crowd know I won this fight. He's not the champion. That's not justice. He's going to take that belt, and it's going to be a lie," Periban said.
He added: "It was definitely a strong fight. I showed my best against him, and I deserved to win. I'm a better boxer, a cleaner boxer. He started the head butts. He even hit me in the neck one time."
Bika admitted that his opponent had him in trouble in the 12th but believed his experience of the championship rounds allowed him to see things out to the final bell.
He said: "It was very hard to survive. I always work hard. When you are working hard, everything comes out right."