The American, who beat Roger Federer in the Swiss great's last competitive match on Friday, proved a fly in Europe's ointment once again with a scintillating victory.
He was outplayed in the first set but roared back to win 1-6 7-6(11) 10-8 to give Team World an unassailable 13-8 lead.
Team World, who had lost the four previous editions of the team event, began the day trailing 8-4 but Canada's Felix Auger-Aliassime (22) stunned Novak Djokovic (35) 6-3 7-6(3) having earlier partnered Jack Sock (30) to a 2-6 6-3 10-8 victory against Andy Murray (35) and Matteo Berrettini (26).
Tsitsipas had the chance to take the match to a deciding singles, but Tiafoe was inspired in front of a raucous O2 Arena crowd who loved his showman antics.
After winning the match point he collapsed to the court and was buried under a pile of his team mates and captain John McEnroe who then treated the crowd to some dance moves.
"It's an unbelievable feeling," Tiafoe, who reached the US Open semi-final said on court. "John McEnroe dropped a lot of F bombs saying we can't lose again. Felix beat Novak today and we all did it together, it wasn't just me."
McEnroe was clearly overjoyed to finally end a long wait to taste victory and get one over old rival Bjorn Borg who was captain of a Team Europe side who were big favourites.
"No one beats Team World five times in a row," the American said. "Felix stepped up big time.
"Frances is prime time, we saw that at the US Open.
It was not the ending Federer had dreamed of in the last event of his 24-year professional career.
Apart from playing his last-ever competitive match, he had sat at courtside in every match here, offering his words of wisdom and support to his team mates.
"This is an incredible team event and I'm loving every second of it."
"I was on the team. Almost lost my voice. My hands hurt from clapping. Told Andy (Murray) in the locker room, I don't like losing. It's not fun.
"This weekend has been all over the place for me. I enjoyed it, but it's unfortunate that we couldn't get the win tonight."
Tiafoe, beaten heavily by Djokovic the previous evening, was making no apologies to Federer for being the pantomime villain.
"Absolutely not. I'm not going to apologise to him. He's got a lot to apologise after the last 24 years after beating everybody on the tour," Tiafoe, clutching a beer, said.
"But I will say thank you for having me in this amazing event, for what he's done for the game. He's a class act. Happy to know him, happy to call him friend, happy to call him a colleague, and best wishes in his second act."
Team World will be aiming to retain their title next year when the event takes place in Vancouver.
