The Belgians had a few anxious moments on the back nine Sunday but held on to shoot a 4-under 68 and claim a three-stroke win, despite a determined late run by Australia and Mexico.
The sunny skies and lack of wind on Sunday was a far cry from Friday, when driving rain and gusty winds meant there were more scores in the 80s than in the 60s.
Belgium shot 71 on Friday, tied for the low score of the day and one of only four scores under par, and shared the lead going into the third round. Many golfers said the Friday conditions were the worst they had ever played in.
Pieters and Detry shot 63 in much-improved weather on Saturday in the four-balls (best ball) and took a five-stroke lead into the final round of foursomes at Metropolitan.
From there, it was a case of hanging on for the $1.12 million in prize money they each received.
"It was a long back nine" Pieters said while surrounded by family, friends and fans, some with Belgian flags stuck on their heads, just off the 18th green.
Australia's Marc Leishman and Cameron Smith pulled to within two strokes late in the round, thanks to holing out from the bunker for a birdie by Smith and a 12-foot par save on the next hole by Leishman.
"Belgium was clearly the best team all week,'' Leishman said. "When you come up against someone like that, we did what we had to do to put the pressure on, and they were just too good."
If there was any doubt, Pieters' approach to 4 feet on the 18th set up a final birdie by Detry to give the Belgians a 23-under total of 265.
"We were both nervous at times, but to finish with a birdie was special," said Pieters.
Leishman and Smith shot 65. Mexico's Abraham Ancer, who won last week's Australian Open, and his partner, Roberto Diaz, playing in the last group with Belgium, shot 66 and also pulled to within two strokes of the lead but finished tied with the Australians for second.
Pieters is from Antwerp and Detry from Brussels. Pieters says news of their win will likely "go very under the radar" in both cities. But he has hope for the future for golf in his soccer-dominated country.
"Hopefully it will make the news, but it's different in Belgium," Pieters said. "Golf is very different than Australia or the U.S. It will get in the media and they'll see us cool guys."