Opener David Warner hit an unbeaten fifty but could not take Australia past the finish line as the visitors blew a comfortable chase to allow South Africa secure a 12-run victory in the second Twenty20 on Sunday.
South Africa posted a below-par 158-4 in their 20 overs after Australia put the brakes on their scoring, but managed to defend the total as the Port Elizabeth wicket slowed up.
Warner was unbeaten on 67 from 56 balls and could only watch as saw Australia, who were 98-1 in the 13th over, found a way to stumble to 146-6.
The series is level at 1-1 with the decider to be played in Cape Town on Wednesday, after which the sides will play a three-match ODI series.
Captain Quinton de Kock was the mainstay of South Africa's innings, his five fours and four sixes forming the backbone of a fine 70 from 47 balls before he got caught at mid-off.
Rassie van der Dussen (37 from 26 balls) provided a vital contribution, but South Africa were 20 or so runs short of where they should have been, having scored only 36 runs in the last five overs despite wickets in hand.
Seamer Kane Richardson was the pick of the Aussie bowling attack with 2-21 in four overs.
Australia appeared to be cruising in their reply and when Steve Smith (29 from 26 balls) was out with the score on 98, they needed 61 from 45 balls with eight wickets remaining.
But South Africa used the slow wicket expertly as wrist spinner Tabraiz Shamsi returned figures of 0-17 in his four overs to increase the pressure on the visitors.
Australia needed 20 from the final 12 balls and when Kagiso Rabada’s penultimate over went for only three, they were firmly on the back foot and never recovered momentum.
