The Kangaroos, opting to field first, restricted the 2014 champions to 154-6 in their 20 overs.
Wicketkeeper-batsman Kusal Parera made 35 from 25 balls with the help of four boundaries and a six.
Australia put on an all-round stellar performance to celebrate about! 🎉@RoyalStaglil | #InItToWinIt pic.twitter.com/QNmvHk3Z9f
— ICC (@ICC) October 28, 2021
Charith Asalanka hit four boundaries and a six as well on his way to 27-ball 35.
Bhanuka Rajapaksa made 33 from 26 deliveries with four fours and a six.
Mitchell Starc, Pat Cummins and Adam Zampa got two wickets each.
It took 17 overs for Aaron Finch’s side to complete the run chase.
Warner played a match-winning knock of 65 from 42 balls with 10 boundaries to his name.
He put on a 70-run opening partnership with skipper Aaron Finch, who made 37 runs off 23 deliveries with five fours and two maximums to his name.
Wanindu Hasaranga de Silva bagged two wickets.