"It feels so good," said the American, who claimed his third tour title, his first since the 2018 Sony Open.
"I've worked really hard and underachieved for quite some time. It feels good to be back doing me."
Kizzire had a four-shot overnight lead at Silverado Resort in Napa, California, and his two-under effort gave him a five-shot victory over David Lipsky.
He had missed the cut in his past two starts and failed to make the FedEx Cup playoffs, which culminated with the Tour Championship last month.
Kizzire holed out from the greenside rough for eagle at the par-five fifth hole, but he bogeyed the ninth and 11th to open the door to Lipsky.
Kizzire rebuilt his lead with birdies at the 12th, 13th and 15th as Lipsky settled for a one-under par 71 and a 72-hole total of 273.
"David played great," Kizzire said. "He applied some pressure to me, I just stayed disciplined.
"I've worked really hard, and to come out and play like I did - and pull away from the field and keep the pedal down and play like I can play - that was so much fun."