South Africa lost by 17 runs in Sunday's clash at Marrara Oval, bowled out for 161 after Australia were dismissed for a disappointing 178 from the final ball of an innings rescued by Tim David's 83.
South Africa's innings was built around 71 in 55 balls from wicketkeeper and opening batsman Ryan Rickelton.
Josh Hazlewood was the hero for Australia, claiming 3-29, while veteran legspinner Adam Zampa finished with 2-32 from his four overs.
Opening the bowling, offspinner Glenn Maxwell took 1-29 from four overs and claimed a typically spectacular leap-over-the-boundary and toss-the-ball-in-the-air catch to get rid of Rickelton in the final over.
Australia have now, unprecedentedly, won 23 of their last 27 T20Is including a 5-0 clean sweep in the Caribbean last month.
The Proteas had managed only six wins from their previous 13 matches and had not won any of their last three bilateral series.
Wild batting saw Australia collapse to 6-75, attempting to cash in on fielding restrictions during the first six overs, but a bad miss in the field allowed Tim David to salvage matters, hitting eight sixes in his 52-ball innings while batting with the tail.
David was given a costly life on 56 when he skied spinner Senuran Muthusamy to long on, only for Tristan Stubbs to drop a straightforward outfield catch. The next two balls went for six.
Australian captain Mitchell Marsh set the tone by smashing the first ball of the match, from Lungi Ngidi, over long off for six after South African captain Aiden Markram won the toss and chose to bowl.
But Travis Head (2) went in the second over and new No.3 Josh Inglis for a first ball duck in the third.
Marsh (13) skied Kagiso Rabada to Kwena Maphaka at deep square leg, Cameron Green (35 in 13 balls) skied Ngidi straight up in the air and Mitch Owen (2) played the worst shot of the night, charging Maphaka to lose his off stump.
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