The hosts, who turned in a poor batting display in the opening game when they set 120, were equally poor on Wednesday in managing to set 121 for victory with Juan Theron grabbing four wickets for 27.
The Proteas cruised for most of the response with Graeme Smith (38) and Colin Ingram (32) helping their side cross the line with 10 balls to spare.
After winning the toss and electing to bat first, Pakistan's innings bore several similarities from 24 hours earlier.
They lost wickets in clusters, there was poor decision making and they had to again rely on newly appointed Test captain Misbah-ul-Haq (33) to see them to a respectable total.
Shahzaib Hasan (six) was first to go when he mistimed a Lonwabo Tsotsobe delivery straight to Johan Botha, running back from midwicket.
Mohammad Hafeez (14) managed two fours during his brief stay but was then in two minds to Morne Morkel's second delivery and was bowled.
Imran Farhat (nine) suffered the same fate - misjudging a slower Tsotsobe ball with the consequences being a lost leg stump.
A silly run out accounted for Umar Akmal (five), who was looking for a second run but sent back by Misbah, and skipper Shahid Afridi (three) again played an irresponsible shot that flew in the wrong direction with Smith taking a good catch at deep cover.
That left Pakistan at 39 for five and with plenty to do in order to stay in the game.
Misbah and Abdul Razzaq (25) tried their best in a 45-run stand which took the better part of eight overs, but after the latter smashed Albie Morkel for a six, he fell next ball.
His partner tried to fight a lone battle with his side crossing 100 in the 18th over - the longest it has ever taken them in T20 cricket surpassing the mark set on Tuesday.
He was eventually out in the last over when Theron claimed three wickets from the final four balls to leave the hosts at 120 for nine.
Pakistan needed early wickets, but got none as Smith and Loots Bosman (11) put on 38 for the first wicket, before Afridi came in and struck immediately.
The skipper should have then had the wicket of Smith in the ninth over, but Akmal spilt a regulation chance at long-off.
AB de Villiers also fell for 11, before Afridi ended his miserly spell with one for 13.
There was a little more pressure when Smith was stumped with 53 still needed from 40.
But JP Duminy (22 not out) along with rookie Ingram took them to their sixth consecutive T20 win.