Nishikori breezed to a 6-2 6-3 victory over Lopez in a match that lasted just 67 minutes, not much longer than his outing on Saturday when he advanced to the final after Marinko Matosevic was forced to retire with a foot injury following the first set.
A well-rested Nishikori broke Lopez's service twice in the opening set to move ahead 4-1 then took control in the second by opening with another break.
"I'm very happy with the way I played," Nishikori said. "To win this title is an amazing feeling. Hopefully I can win a couple more titles. It's been a good start to the year."
It was the third career title for Nishikori, who also won the Japan Open in Tokyo last October to become the first Japanese player to win on home soil.
Lopez never recovered from a rough start and missed a chance for his first win since 2010.
"He was very aggressive from the beginning," Lopez said. "I have no regrets. I tried everything I could and he was just the better player today."
In the women's final, New Zealander Marina Erakovic has seen her WTA singles ranking improve nine places after German Sabine Lisicki retired through injury.
Lisicki boweed after losing the first set 6-1, and the result marks Erakovic's first WTA tour title.
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- Marinko Matosevic