South Africa 165 for 7 (Markram 39, Adair 3-39) beat Ireland 132 for 9 (Tector 36, Shamsi 4-27, Ngidi 2-18) by 33 runs
Dublin: South Africa claimed a 33-run win over Ireland in the first of three Twenty20 games between the sides this week.
Aiden Markram top-scored with 39 and David Miller added 28 as the tourists made 165-7 at a sunny Malahide in Dublin after being sent in to bat.
Ireland were soon in trouble at 46-5 in reply, with Harry Tector (36) offering resistance before an unbeaten last-wicket stand of 44.
Spinner Tabraiz Shamsi took 4-27 as the hosts fell short on 132-9.
The teams played out a 1-1 draw in the ODI series before starting the T20s on Monday, with the final two games at Stormont in Belfast on Thursday and Saturday.
Proteas captain Temba Bavuma (13) and Quinton de Kock, whose 20 came off nine balls, provided a solid start.
It was built on by the middle order as Markram, Rassie van der Dussen (25) and Miller set South Africa up for a decent total.
Ireland paceman Mark Adair finished with 3-39, while Simi Singh (2-19) and Josh Little (2-27) both chipped in with two wickets.
Big-hitting opener Paul Stirling smashed a six, but lasted just two balls before a first-ball duck for partner Kevin O'Brien.
Ireland never recovered from the poor start with skipper Andrew Balbirnie (22) and Tector the only ones to reach double figures before a valiant 10th-wicket partnership.
Barry McCarthy (30) and Little (15) were still there at the end as the Irish gained some pride in defeat.