The 21-year-old is one great round from becoming the youngest victor of a World Golf Championships (WGC) event, as well as the first to win in his first WGC start.
World No. 20 Rafa Cabrera Bello fashioned a 4-under-par 33-34=67 in the final round of the WGC-Mexico Championship to wrap on 15-under 269, down one place to T3, one swing short of a two-man playoff involving Justin Thomas and eventual champion Phil Mickelson.
Sharma would also be the first player to win on his PGA Tour debut since Jim Benepe at the 1988 Western Open, eight years before the Indian was born.
"Winning is everything. I mean, there is no better feeling than when you think you sink that winning putt". I knew it was going to be soon, I was playing too well for it not to be, but you just never know until it happens. You know, I met him for the first time today and it's great that I'm paired with him tomorrow.
Sharma broke through with his maiden victory at the Joburg Open in December and followed up with another triumph at the Maybank Championship in Malaysia last month where he came from four shots back to win with a closing 62.
It nearly was too good to be true.
Mickelson and Thomas started their playoff on the par-3 17 hole.
Thomas was seeking his eighth victory in his past 32 PGA Tour starts.
Shubhankar: 'Mickelson thought we were media at first'
Thomas sat in the 18th fairway in a four-way tie for the lead. Mickelson's 18-foot birdie putt for the victory swirled around the cup, more agony for a 47-year-old who has seen plenty of it since his last victory.
The American pair finished tied on 16 under par after an enthralling final round at Chapultepec Golf Club.
"He thought we were media and he said, "not right now, after the round", Sharma said of the World Golf Hall of Famer.
Sharma holed a 15-foot par putt on the final hole at Chapultepec Golf Club for a 2-under 69, leaving him 18 holes away from capping off his wonderful rise.
Overnight leader Shubhankar Sharma of India crashed out with five bogeys in a final round 74 to finish tied for ninth at 274.
Another shot back was Dustin Johnson, the No. 1 player in the world and defending champion, who managed a 68 despite playing the par 5s on the back nine in 1 over.
After finding the fringe at the driveable first hole, the Indian chipped home for eagle from 10 yards. Even golfers who play on the European Tour with Sharma are still unfamiliar with his rise up the rankings.