Set 188 to win, New Zealand never really recovered after regular setbacks and eventually finished on 154 for 8 from their 20 overs.
Bevon Jacobs top-scored with 36 off 19 balls, while James Neesham made 24 and Tim Robinson added 25. But South Africa’s bowlers kept chipping away, with Gerald Coetzee, Wiaan Mulder and Ottneil Baartman taking two wickets each.
Earlier, South Africa posted a competitive 187 for 4 after a late onslaught from Connor Esterhuizen, who smashed 75 off just 33 deliveries. He dominated the closing overs with five fours and six sixes, turning a solid platform into a commanding total.
Before Esterhuizen’s fireworks, Rubin Hermann made 39 and Mulder chipped in with 31 to steady the innings. Dian Forrester then provided useful late support with an unbeaten 21.
For New Zealand, Ben Sears claimed two wickets, while Zak Foulkes and Josh Clarkson picked up one apiece.
The result handed South Africa a comeback series triumph after trailing earlier, with the visitors finishing strongly to clinch the five-match contest 3-2.
