The previously unbeaten Alvarez began by attempting to slow down Mayweather with stiff jabs and hooks to the body, but in response Mayweather (45-0, 26 KOs) snapped back his head with jabs of his own.
The more Alvarez (42-1-1, 30 KOs) stepped forward and became aggressive, the more he left himself vulnerable to Mayweather's rapid counterpunches.
After a relatively quiet opening few rounds, Mayweather began to open up in the fourth, snapping back Alvarez's head with a succession of jabs and then landing a sweeping right at the bell.
In the fifth, Mayweather stood in the pocket in front of Alvarez and landed a series of combinations that rattled his opponent.
When Alvarez attempted to pin Mayweather in the corner in the seventh, the American slipped most of his punches and answered with a right hand, followed by a sequence of jabs and an uppercut, before backing the Mexican to the ropes and picking him apart.
It was the same in the 10th, Mayweather turning defence into offense as he landed counters off the ropes and sent Alvarez into retreat.
"I think if I had pressed the attack earlier, I could have got the stoppage. I like taking my time. But it was a great fight," five-division world champion Mayweather said.
By the end, Alvarez cut a forlorn figure, following Mayweather around the ring as his foe retreated and circled to lure him into a trap.
The final result appeared a formality, and it was a surprise when one of the judges scored the bout a draw.
She was overruled by scores of 117-111 and 116-112, which also seemed close but may have reflected the fact that Mayweather, seemingly confident of victory, effectively coasted through the final couple of rounds.
"I couldn't connect," Alvarez conceded. "He was very elusive and intelligent. He has a lot of experience and I honestly couldn't find him. In the late rounds, I was frustrated. I recognize he beat me. He's a great fighter."
Mayweather praised his fallen foe.
"I fought a true champion tonight," he said. "A guy like that can take a loss and bounce back from it. I've been in the sport 17 years, so just because I beat him the way I did, doesn't mean he doesn't have a great career ahead of him."
(Editing by Amlan Chakraborty)
