South Africa's David Miller hit an unbeaten 75 to help the tourists out of early trouble before their spinners then restricted Ireland to secure a 42-run victory in the second Twenty20 international at Belfast.
Miller was in belligerent mood, scoring off 44 balls, to lift South Africa to 7-159 on Thursday after they won the toss and elected to bat.
Ireland were bowled out for 117 in reply as spinners Tabraiz Shamsi and Bjorn Fortuin took three wickets each.
South Africa lost two wickets in the first four balls of the innings and were in trouble at 5-58 but Miller led a fightback, taking full advantage of being dropped on 19 to see them to a respectable score. He hit four sixes in the final over.
Ireland failed to gain any traction in their reply and were strangled by the spinners with Shamsi underlining his ranking as the top T20 international bowler with 3-14 off his four overs.
Fortuin took 3-16 while Shane Getkate top scored for the Irish with 24 before they were bowled out with three balls to spare.
South Africa won the first T20 international in Dublin on Monday by 33 runs with the last game of the series also in Belfast on Saturday.