England chased down South Africa's 179/6 with two balls to spare.
Asked to bat first, South Africa posted 179/6 in 20 overs on the back of Faf du Plessis’ 40-ball 58 and notable thirties from Rassie van der Dussen (37 off 28 balls) and captain Quinton de Kock (30 off 23 balls).
Sam Curran was the stand-out bowler for England, claiming 3 wickets by conceding 28 runs in his four overs.
In reply, the visitors rode on Jonny Bairstow’s unbeaten 48-ball 86 to overhaul the target with five wickets and four balls to spare.
For South Africa, George Linde (2-20) and Lungi Ngidi (2-31) picked up two wickets each.
Speaking after the match, England skipper Eoin Morgan said he was extremely pleased with the win while chasing a stiff target.
“Extremely pleasing. It was a very good win given we were pretty average apart from two or three guys. Jonny's had an unbelievably good day out on a wicket that was a little bit two-paced. Also, South Africa posted an above-par score, chasing was always going to be difficult. Being three down early poses challenges,” Morgan said at the post-match presentation ceremony.
“Jonny and Ben set up the chase nicely. When you win games of cricket like that one, when you don't necessarily play your best cricket, it's extremely pleasing. The more time we spend together, the more we play, the more we get used to the roles that we play. It's beginning of the tour, nice to start with a win. Hopefully, we'll improve and progress in the next few games. We need to be doing the right things,” he added.
Reflecting on the loss, Proteas skipper De Kock said: “We did think it was a good total with the way our guys batted, but it just didn't come right tonight. I don't necessarily think it was just that one over, but the way Jonny and Stokes batted was superbly. Jonny batted really well today. Very happy with the way Linde was bowling in the nets; happy for him and it was a good day for him. Just one or two small things in the field we could've done better.”
The second T20I will be played in Paarl on Sunday (November 29).