It was Djokovic's 15th win over the Del Potro and fifth in five at the Slams.
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.
Mats Wilander dropped a major praise on Novak Djokovic after the Serbian's win at the 2018 US Open, comparing him to Roger Federer and Rafael Nadal. 'His movement is so good.
Despite the typically enthusiastic backing of his fellow Argentinians, Del Potro was denied a second U.S. Open title nine years after his dramatic 2009 triumph.
Naomi Osaka jumped 12 places to a career-high No. 7 in the WTA standings thanks to her first Grand Slam title. But supported by a dozen or so friends from back home, whose "Ole!" choruses rang around the arena, he climbed up the rankings to a career-high No. 3 by thundering his 100 miles per hour (160 kph) forehands and 135 miles per hour (215 kph) serves.
It is his 14th Grand Slam title, which ties him with Pete Sampras for third on the all-time major singles titles list behind Federer's 20 and Nadal's 17.
While Djokovic laid on the ground in ecstasy Sunday, del Potro sat in his chair and cried.
The WTA is calling for fair treatment of women's players and coaching to be allowed across tennis in the aftermath of the U.S. Open women's final.
"I would like to congratulate Juan Martin on what he has done in the last 4-5 years with his wrist injuries and coming back and still having faith and belief in himself that one day he's going to be a top player and he is going to fight for Grand Slam". He knows he is one of my friends on Tour and knows he is one player I want to see win titles.
Del Potro, the No. 3 seed from Argentina, advanced in Friday's other semifinal when defending champion Rafael Nadal retired from their semifinal because of a painful right knee after dropping the opening two sets. Del Potro misses a backhand giving Djokovic another game point, but Del Potro saves it with a scintillating forehand that Djokovic can't get it into the court. "I'm glad that Novak is the champion".
But he had a 4-14 losing record against Djokovic, including four at the Slams - two of them at the US Open in 2007 and 2012.
Novak Djokovic says he thinks the chair umpire interfered too much in Serena Williams' match but stopped short of saying men and women are treated differently. He depended on his hometown friends, a group of whom have been in NY throughout the fortnight to lead cheers in Arthur Ashe Stadium, and worked his way back to the final at his favorite ATP Tour event.