LAS VEGAS (AP) – Floyd Mayweather Jr. couldn’t win over the crowd, or even his own father. All he could win was the only thing that really counted Saturday night, his fight against Oscar De La Hoya.

Boxing’s bad boy beat the Golden Boy in one of the richest fights ever, using his superb defensive skills and superior speed to take a 12-round split decision and win the WBC 154-pound title in his first fight at that weight.

He didn’t impress the pro-Mr. De La Hoya crowd that roared with every punch thrown by their hero, and even Floyd Mayweather Sr. thought his son had lost. But Mr. Mayweather landed the harder punches and landed them more often, and that was enough to eke out yet another win.

“It was easy work for me. He was rough and tough, but he couldn’t beat the best,” Mr. Mayweather said. “I was having fun in there. It was a hell of a fight.”

The fight that was supposed to save the sport may not have done that, but it was entertaining enough and competitive enough to keep everyone’s attention even though neither fighter seemed to hurt the other and neither went down.

Both proud champions fought from the opening bell to the end of the final round, which finished with the brawl Mr. De La Hoya wanted all along. But it came too late to help Mr. De La Hoya, who lost four of the last five rounds on two scorecards, sealing his fate.

“I could see I was hurting him,” Mr. De La Hoya said. “I was pressing the fight, and if I hadn’t pressed the fight there would be no fight. I’m a champion, and you have to do more than that to beat a champion.”

Mr. De La Hoya threw far more punches than Mayweather in an almost desperate bid to overcome Mayweather’s slippery defense. He trapped Mr. Mayweather on the ropes and in the corner almost every round, throwing flurries to his head.

But many more missed than landed, allowing Mr. Mayweather to dance away, often after countering with a punch or two of his own.

“I just fought the best fighter in our era and I beat him,” Mr. Mayweather said.

The sellout crowd of 16,200 that paid a record $19 million gate didn’t think so, booing the decision just as it had booed Mr. Mayweather when he came into the ring wearing a sombrero on Cinco de Mayo.

And neither did Floyd Mayweather Sr., the estranged father of the undefeated champion and the former trainer of De La Hoya.

“I thought Oscar won the fight on points, threw more punches and was more aggressive,” said the senior Mr. Mayweather, who munched popcorn as he watched the fight from a $2,000 ringside seat given to him by Mr. De La Hoya. “My son had good defense and caught a lot of his punches, but I still thought Oscar pressed enough to win the fight.”

Two of the three ringside judges, though, gave the fight to Mr. Mayweather, who has never lost in his pro career and won a title for the fifth time in as many weight classes.

Mr. Mayweather was favored 116-112 by judge Chuck Giampa and 115-113 by judge Jerry Roth. Judge Tom Kaczmarek had De La Hoya ahead 115-113. The Associated Press had Mayweather winning 116-112.

Because this was boxing, the fight didn’t end without some controversy. Mr. De La Hoya’s corner said it might protest the decision after noticing that the scorecards circulated at ringside had the fighters in the wrong color corners, but the director of the Nevada Athletic Commission said they were correct.

The fight lacked the drama of the slugfest that Mr. De La Hoya wanted when he offered Mr. Mayweather a chance to make at least $10 million to fight him for the title. De La Hoya made at least $25 million for only his third fight in the last three years.

Mr. De La Hoya wanted Mr. Mayweather to trade punches in the middle of the ring with him, thinking he would win the fight on power against a fighter who moved up in weight to challenge him.

“The champion in me wanted to stop him,” Mr. De La Hoya said. “I was just trying to close the show.”

The fight ended with the crowd on its feet and two fighters trading punches wildly at the final bell. They then stopped and embraced each other.

In the end, Mr. Mayweather was simply faster and more slippery, and landed more punches.

Ringside punching stats heavily favored Mr. Mayweather, crediting him with landing 207 of 481 punches to 122 of 587 for Mr. De La Hoya. Mr. Mayweather also landed more power punches than De La Hoya, outscoring him 138-82.

Mr. Mayweather said before the fight that Mr. De La Hoya would fade as the fight went on, and it seemed as though he did. He used the jab more early, but got away from it from the eighth round on, giving Mr. Mayweather an easier shot at him with right hand leads.

Mr. Mayweather had predicted he would dominate Mr. De La Hoya and give him a beating, but Mr. De La Hoya took his best punches and came back with enough of his own to keep it close. Mr. De La Hoya appeared staggered by a right hand with 20 seconds left in the fight, but finished with a flurry as the crowd erupted in delight.

Actually, the crowd cheered wildly every time Mr. De La Hoya got Mr. Mayweather on the ropes and flailed away. But the punches mostly missed, and Mr. Mayweather hopped away, often giving Mr. De La Hoya a parting shot to the head.

Mr. Mayweather was a 2-1 favorite when the fight was made, but money poured in on Mr. De La Hoya and he was a 3-2 underdog by fight time. Still, there was no doubt who the favorite was among the crowd of celebrities and high rollers who paid $2,000 for ringside seats to watch the spectacle.

Mr. De La Hoya was the aggressor throughout, managing to get through Mr. Mayweather’s defenses in the early rounds as Mr. Mayweather moved away and counterpunched without great effect. Every time Mr. Mayweather went near the ropes, Mr. De La Hoya tried to trap him there and land a flurry of punches to the body and head.

Mr. De La Hoya wanted to get Mr. Mayweather into a brawl, but he was having no part of it, content to pick his spots. In the fifth round, however, the fight seemed to shift into a different gear as Mr. Mayweather stood his ground and landed some hard combinations to the head.

“He’s getting tired. He’s getting tired,” Mr. Mayweather’s trainer and uncle, Roger Mayweather, told his fighter after the round.

It was a night of ebb and flow, with both boxers fighting in flurries and both having their moments. The pro-Mr. De La Hoya crowd roared loudly anytime he threw a big punch, while Mr. Mayweather smiled at his opponent every time Mr. De La Hoya landed a punch that got any reaction from his fans.

In the end, though, Mr. Mayweather’s hand was raised in victory. His father got in the ring with him and they embraced.

And boxing had survived for one more night.