Ross Adair became the third Irishman to score a century in a T20 international as he hit 100 off 58 balls to help Ireland to 195-6 after being put into bat at the Zayed Cricket Stadium.
Mark Adair took 4-31 in his four overs as Ireland then put the brakes on the reply when the South Africans looked on course to successfully chase down the imposing target.
South Africa lost their last six wickets cheaply, with Adair taking three in his last over, to finish on 185-9.
Ireland got off to an impressive start with a 137-run opening wicket partnership between Ross Adair and skipper Paul Stirling, who made 52.
Adair’s nine sixes in his innings broke Stirling’s Irish T20 record of eight.
South Africa’s top order were hauling in the target as Reeza Hendricks and Matthew Breetzke both made 51 and Ryan Rickleton 36.
But when key batsman Tristan Stubbs went cheaply on 157-4 with four overs remaining, the South African innings collapsed to offer the Irish victory.
Ireland and South Africa will now play three One Day Internationals in Abu Dhabi, starting on Wednesday.