Ireland made one change to the side from Friday, with Graham Hume replacing Craig Young.
South Africa won the toss and elected for Ireland to bat first.
With regular opening batsman Andrew Balbirnie sitting out the T20 encounters, Ireland, as they did on Friday began the game with the top-two pairing of Ross Adair with Paul Stirling.
The two formed a formidable partnership with a 137-run opening stand, Ireland’s second biggest in T20 format.
It included a half century for Stirling alongside Adair’s brilliant century, which was only Ireland’s third in this format.
Adair managed 100 from just 58 deliveries, hitting nine sixes and five fours.
George Dockrell managed 20 and Harry Tector added five runs as Ireland moved to 195, their highest T20 total against South Africa.
The second innings was all about another Adair, this time brother Mark.
He bowled out claimed Matthew Breetzke, Tristan Stubbs, Wiaan Mulder and Nqaba Peter claiming two wickets in three deliveries at one stage to help Ireland to the famous victory.
More to follow.