The win is the fourth WTA title for the Ukrainian world number 19, who won 6-7(5) 6-4, 7-5 over Bouchard, of Canada.
The third set was hit by intermittent suspensions of more than two hours due to Kuala Lumpur’s tropical rains.
Down early in the set, the sixth-seeded Bouchard managed to claw back into a tie at 5-5, but once play resumed for good the second seed Svitolina put the contest away.
It was Svitolina’s third victory in as many meetings with Bouchard and her first since winning the WTA Marrakech in May of last year.
Bouchard, however, took another step toward regaining her form after a rough season last year.
She rose to as high as world number five in late 2014, with a series of solid Grand Slam showings under her belt.
But her form dropped off in 2015, and she slipped in the locker room at the US Open in September, suffering a concussion.
Forced to pull out of the tournament, she missed three months of play, but has shown signs lately of getting back on track.
The doubles competition was won by the Varatchaya Wongteanchai of Thailand and Yang Zhaoxuan of China, who beat the Chinese duo of Liang Chen and Wang Yafan, 4-6, 6-4, 10-7.