Pakistan medium-pace bowler Faheem Ashraf sparked a South African collapse in the fourth and final Twenty20 international at SuperSport Park in Centurion on Friday.
Faheem took three for 17 as South Africa, who were put into bat after losing the toss, were bowled out for 144 on what is usually a high-scoring ground.
South Africa had reached 73 for one after the early loss of Aiden Markram when Faheem had Janneman Malan caught at mid-off for 33 in the ninth over.
Faheem followed up with the wickets of South African captain Heinrich Klaasen and George Linde. He bowled his four overs in succession and did not concede a boundary.
Fast bowlers Hasan Ali and Haris Rauf took three for 40 and two for 18 respectively.
Rassie van der Dussen top-scored for South Africa with 52 off 36 balls.
Pakistan, who lead the series 2-1, chased down a target of 204 with nine wickets and two overs to spare on the same ground two days earlier.
Their captain Babar Azam, who scored 122 in that run chase, named an unchanged side while South Africa made two changes.
All-rounder Wiaan Mulder and left-arm spinner Bjorn Fortuin came into the side, replacing batsman Pite van Biljon and left-arm fast bowler Beuran Hendricks.