David Warner made 49, while Matthew Wade smashed a 17-ball unbeaten 41 and Marcus Stoinis was not out on 40 off 31 deliveries as Australia overhauled the target with an over to spare.
Earlier, Pakistan made a total of 176/4 on the board.
Openers Mohammad Rizwan and Babar Azam added 71 runs for the first wicket. The duo broke a couple of records while batting together for 10 overs.
While Rizwan became the first batsman to score 1000 runs in T20Is in a year, Babar surpassed Virat Kohli to become the quickest batsman to score 2500 runs in the shortest format.
The final will take place on November 14.