Mike Alvarado gained revenge for his defeat to Brandon Rios in 2012 with a unanimous points victory in their rematch on Saturday night in Las Vegas.
Alvarado provided a strong finish in the closing stages of the 12-rounder to get the nod 115-113 on two of the scorecards, the third judge at ringside scoring it 114-113 in his favour.
The result means the 32-year-old American now holds the interim WBO light-welterweight title. It also avenges his loss to the same opponent five months ago - the only blemish so far on his 34-fight record.
Rios had stopped his compatriot in the seventh last October and a similar outcome looked a possibility as the pair stood toe-to-toe in the opening stages of the bout at Mandalay Bay.
However Alvarado switched his strategy during the middle rounds, instead opting to box and move as Rios chased him around the ring.
His switch proved decisive as he overcame a nasty cut on his forehead to finish much the stronger - then immediately offered Rios the chance to fight again.
"Brandon gave me a shot to redeem myself," Alvarado said. "I'll give him a shot for the trilogy."
The previously unbeaten Rios was also keen for a third chapter, though promoter Bob Arum suggested both boxers might have to wait a little while yet to square off again.
"Are these guys going to fight again?" Arum asked. "Of course they will. But it doesn't necessarily have to be next."