He shares then from now on the third place of the all-time Grand Slam winners list with American player Pete Sempras, but remains at six units behind recordman Roger Federer with 20 trophies to his credit.
Djokovic is now behind his contemporaries Rafael Nadal and Roger Federer in terms of total number of grand slams won.
For Djokovic, he got better as the tournament progressed. He won Wimbledon and a Masters event in Cincinnati.
The Serb now leads del Potro 15-4 in career meetings, and 5-0 in Grand Slam encounters.
The atmosphere ignited again in the second set when Del Potro broke back to level at 3-3, before Djokovic silenced them with a courageous hold - after a 20-minute game lasting 22 points and in which he saved three break points to level at 4-4.
His 6-3, 7-6 (4), 6-3 defeat to the Serbian was not the fairytale outcome he had imagined.
However, Del Potro and his mighty forehand came to the party, striking back in spectacular fashion to level at 3-3, while the support for the giant Argentine appeared to rattle Djokovic's concentration levels. But then he was broken in his next game.
Del Potro - the third seed - had earlier lauded Djokovic, telling ESPN: "So happy to play in the final against this magnificent idol".
Novak Djokovic of Serbia celebrates with his wife Jelena Djokovic after winning his men's Singles finals match.
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"I really am. I feel like these guys, rivalries with these guys, matches with Federer and Nadal, have made me the player I am, have shaped me into the player I am today", Djokovic said, his shiny silver U.S. Open trophy resting a few feet away.
But Djokovic is almost six years younger than Federer and - prior to a two-year barren spell that was ended by his Wimbledon triumph - had been winning slams at an average of almost two a season.
Djokovic added: "I would like to congratulate Juan Martin for what he's done in the last four, five years".
For Djokovic, this has been a triumphant summer after his difficulties of the past two years and the low of elbow surgery in February. He also added five USA and two Australian Open titles, plus a solitary French Open crown in 1996.
U.S. Open champion Naomi Osaka tweeted she was "grateful" for her opportunity to play Serena Williams.
Djokovic will now set his sights on conquering a different summit by reclaiming his place atop the world tennis rankings for the first time since October 2016.
'I'll have some probably now, ' Millman said.
She posed with her trophy at Top of the Rock Observation Deck at Rockefeller Center.
No. 1 Simona Halep retained the top spot even though she became the first No. 1 seed to lose in the first round of the U.S. Open, and Caroline Wozniacki stayed at No. 2 after her second-round exit.