They then bowled out South Africa for 96, just seven more than the host country\'s record low in Johannesburg.
As in Johannesburg, left-arm fast bowler Mitchell Starc bowled De Kock, South Africa\'s star batsman, in the first over of the home team\'s reply.
He followed up by dismissing former captain Faf du Plessis in the third over and was named man-of-the-match after taking three for 23.
Finch was named man of the series for his aggressive batting and astute captaincy.
\"The guys have bought into the roles they have been asked to play,\" he said.
It was the first time Warner and Steve Smith had played at Newlands since both were banned for a year after a ball-tampering scandal at the same ground two years ago.
South Africa were never in the game after Warner and Finch thrashed 120 for the first wicket off 74 balls.
Apart from some powerful hitting by both players, they forced the South Africans into fielding errors with their aggressive running between wickets.
\"It\'s something we pride ourselves on,\" said Finch.
\"It\'s quite disappointing the way we lost,\" said De Kock. \"We have to keep our heads up and keep looking forward.\"
Although Finch said he would have batted if he had won because of the dryness of the pitch, De Kock said he would make the same decision to bowl again.
He said he still thought chasing a target at Newlands was a preferred option, but admitted: \"Australia were 20 runs above par.\"
The six-over powerplay showed the gulf between the teams.
Finch and Warner scored 75 without loss in their powerplay while South Africa were already far behind the required rate at 50 for two after six overs.
It then got worse for South Africa as spinner Ashton Agar (three for 16) and Adam Zampa (two for 10) worked their way through the middle order with no South African able to score more than opener Rassie van der Dussen\'s 24.
Earlier, a no-ball which reprieved former captain Steve Smith proved expensive. Smith was bowled by Kagiso Rabada at the start of the 19th over but replays showed Rabada had over-stepped.
Smith took advantage by hitting 20 runs off the last over bowled by Anrich Nortje, including two sixes, to finish on 30 not out.
