Japan's Nishikori cruised to a 6-2, 6-3 decision over Spain's Lopez, taking only 67 minutes to register the win at the Racquet Club of Memphis.
The fifth-seeded Nishikori improved to 3-2 lifetime in title matches with the victory.
Lopez, meanwhile, fell to 2-6 in eight career championship tilts.
2014: NFL Cheerleaders [PHOTOS]
Julius Randle breaks leg during NBA debut