World number three Swede Henrik Stenson also shot a 68 with five birdies and a bogey to finish second but never managed to put Garcia under serious pressure.
"It was great, an amazing week... obviously being the last week of the year and for having Katharina (Boehm) caddie for me," Garcia, who had his girlfriend caddying for him, told reporters.
Stenson, the first man to win the U.S. Tour's lucrative FedExCup series and the European money list double in 2013, had halved Garcia's overnight lead to two on the turn but the Spaniard put paid to his hopes by sinking three consecutive birdies from the 10th.
"I knew Henrik was going to make it difficult for me. He's been playing so amazingly great, and he did," Garcia, 33, said. "He kept hitting good shot after good shot.
"And then when I bogeyed seven, I had to make a good par save on nine after getting a bit unlucky with the approach shot. And then I made three very important birdies on the first three on the back nine and gave myself a little bit of a cushion."
Stenson rued some missed opportunities on Sunday but was not too unhappy with his overall performance during the week.
"I've had a great year but coming here really on the fumes left in the tank, not too much going for me to perform in that sense," the Swede said.
"But I played really nicely yesterday and I was hanging in there today and I was just coming up a couple short."
Frenchman Alexander Levy (69) was four shots behind Stenson at third spot while U.S. Open champion Justin Rose (72), last year's winner Charl Schwartzel (67) of South Africa, India's Anirban Lahiri (73) and Japan's Yuki Kono (69) finished tied for the fourth place.
(Writing by Sudipto Ganguly; editing by Alan Baldwin)
