Proteas opener Connor Esterhuizen finished not out with 45 from 48 in the chase. Mitch Santner had a remarkable T20 figures of 1-8 from his four overs as South Africa had the luxury to pick their spots in the winning chase.
New Zealand won the toss with 32-year-old Nick Kelly making his debut, while South Africa picked four on debut including 19-year-old opening bowler Nqobani Mokoena.
The Black Caps never got their innings going, with Devon Conway dismissed first ball of the first over for a one by Gerald Coetzee. Coetzee then trapped Tom Latham eight balls later, leaving New Zealand 14-2.
Ottneil Baartman then removed both Tim Robinson and Kelly within three balls as the home side slumped to 21-4.
Any plans to get a chance to put his feet up for skipper Mitch Santner were scuppered when he had to walk out in the fourth over. Bevon Jacobs finally hit the first six of the match in the sixth over, only to be removed by a direct hit by Jordan Hermann.
At 36-5, New Zealand’s hope of resurrecting the innings was left to veterans Santner and James Neesham, putting on 18 off 21 before the skipper was bowled by Keshav Maharaj for six.
Teenager Mokoena then dismissed Neesham, Zak Foulkes and Kyle Jamieson to finish with 3-26. When New Zealand’s final wicket fell, Cole McConchie for 15, the innings ended with 33 balls left unused.
Foulkes struck early, dismissing South African opener Tony de Zorzi in the second over but the visitors safely navigated the opening power play and with little run-rate pressure, cruised to victory.
The spin-friendly nature of the pitch even saw fielders placed in close for Santner’s bowling.
“I think there was a little bit more in it than we thought, especially up front,” Santner said after the defeat.
“Also, South Africa bowled really well and put us under pressure from the start. Losing wickets in the powerplay makes it tough from there. I think if you identify that it’s doing a little bit early, you maybe have a look. But again, they bowled well. Being four down in the powerplay is always a challenge.
“We pride ourselves on adapting, and we didn’t do that quickly today.”