Singh two-putted for par on 18 to cap a 3-under 70 and complete the season-opening event at 14-under-par 278. Scott birdied three of the last four holes, but his bogey on the 17th cost him a chance at a playoff. The Australian finished at 12-under-par 280 after a final-round 69.
This is Singh's 30th PGA TOUR win and with that he reached three milestones. He became the 17th player with 30 or more wins in PGA TOUR history. The title was also his 18th since turning 40. That broke the tour record for victories over 40.
Finally, the $1,100,000 winners check pushed Singh over the $50 million mark in career earnings on the PGA TOUR. He is just the second player to break that plateau, joining Tiger Woods, who has over $65 million in career earnings.
'It's still going. It isn't one of those things that you don't really think about until you do it,' Singh said. 'I really proud to get 30 wins. There are a lot of tournaments to go and a lot of years to go and hopefully I can get up to 40 (wins).'
Singh seemed to put things away early. He sank a 5-footer for birdie at the first and made it two straight as his 11-foot birdie putt at the second found the bottom of the cup.
The Fijian led by six at that point and cruised around the turn with eight straight pars. His lead dropped quickly as Will MacKenzie birdied three straight from the second to move to 9 under and within four. MacKenzie fell back later on the front nine, but Scott started to make his move.
Scott slipped back to minus-6 with bogeys at the second and fourth. However, he bounced back with a 19-foot birdie putt on five and a 6-footer for birdie on six.
The Australian dropped in a 6-foot birdie putt at the ninth to make the turn at minus-9, four behind Singh.
Singh responded by converting a 12-foot birdie putt at 11 to push his lead back to four. He parred the next five to remain there.
Scott fought back into the picture with an up-and-down birdie on 15. He came right back with a 10-foot birdie on 16 to move within two of Singh.
The Australian stumbled to a three-putt bogey at the 17th and that dropped him three back.
Singh missed a 13-foot birdie attempt on 17 and two-putted for par at the last, but it was enough to hold off Scott.
'I love this place. I love Hawaii. It just reminds me so much of home,' said Singh, who hails from Fiji. 'Last year I came really close, but I wasn't totally convinced I had it until I hit that third shot onto the green at 18. I told my caddie, 'I think I can two-putt from there.''
Scott two-putted for birdie from just over 40 feet at the last to end two back.
'It was a good start to the year,' said Scott. 'I'm happy with my result obviously. It looked like earlier on I had no chance today, but I kind of had a sniff standing on the 17th tee, but unfortunately hit a poor second putt on 17. All in all, it was a good week and something to build on.'
South African Trevor Immelman closed with his second straight 1-under 72 to finish alone in third at 9-under-par 283.
Davis Love III, the 1993 winner, fired a five-under 68 to share fourth at minus-8 He was joined there by J.B. Holmes (72) and Mackenzie (72). Luke Donald took seventh place at 7-under-par 285 after his third straight 71.
Former PGA champion David Toms closed with the best round of the day, a 6- under 67, to end in a tie for eighth at minus-6. He ended alongside K.J. Choi and J.J. Henry. Stuart Appleby, who won this event the last three years, shared 13th as he closed with three straight rounds under par.