A year after missing the U.S. Open because of an injured right elbow that would require surgery, Djokovic showed that he is unquestionably back at his best and back at the top of tennis.
A focused Djokovic continued to apply pressure in the third set until Del Potro finally cracked on serve to fall behind 5-3, with the Serb closing out the match with a ferocious overhead victor. He won two Grand Slams in one year.
Del Potro - the 2009 champion back for a second slam final after overcoming career-threatening wrist injuries - threw everything he had at his rival, but Djokovic absorbed the Argentinian's power superbly, his returning of serve particularly outstanding.
With the win on Sunday, Djokovic has extended his head-to-head record against Del Potro to 15-4 as the Argentine was unable to upstage the Serb.
Djokovic's victory, coupled with his July triumph at Wimbledon, ties him with Pete Sampras for the most men's Grand Slam singles titles.
Aged just 20, Del Potro defeated Rafael Nadal and Roger Federer in successive matches to win the 2009 US Open, and the world No 3 was determined to stay competitive, staying firm following a gritty hold in the opening game of the next set.
"He's my idol. Pete, I love you", Djokovic said". Not against Djokovic, who always seemed to have all the answers - and who said he convinced himself that all of those "Oles" were actually people calling out his own nickname, "Nole".
Djokovic was better than del Potro on their many lengthy exchanges, using his trademark body-twisting, limb-splaying court coverage to get to almost every ball, sneakers squeaking around the blue court in Arthur Ashe Stadium, where the roof was closed because of rain.
The match's true turning point came in the eighth game of the second set, after Djokovic had lost three straight games and was trailing 3-4 on serve.
Djokovic went on to congratulate Del Potro for his achievements despite all the injury trouble and made a massively sporting gesture by saying he knew Del Potro will stand as champion at this podium one day.
When it ended, thanks to a three-game closing run by Djokovic, he flung his racket away and landed on his back, arms and legs spread wide.
"You can lose or win a trophy, but the love from the crowd, it could be even bigger than the tournament", del Potro said.