A healthy Australia Day crowd of 40,242 turned out for the first international cricket encounter at the Olympic stadium, and even though the home side was helped by an unbeaten 90 when batting first from David Warner, the 3-137 from 20 overs never looked likely to be enough.
Sri Lanka did have a couple of little nervous moments in the run chase, but in the end made the 5-139 in 18.5 overs as captain Angelo Mathews (35 not out) and Thisara Perera (19 not out) saw things home for the tourists who continue to show their quality as a limited overs side.
Australian captain George Bailey won the toss and chose to bat first, but the home side was in early trouble with Aaron Finch out to a terrific diving catch from Kusal Perera off Nuwan Kulasekara for one, and then Shaun Marsh was unluckily run out for six.
Australia was then 2-31 and then 3-53 when Bailey fell for 11 off the bowling of Thisara Perera.
Even though Australia didn’t lose another wicket for the remaining 11 overs, Adam Voges battled to make just 25 from 29 balls without hitting a boundary.
Warner made his highest Twenty20 international score of 90 from just 62 deliveries with five fours and three sixes, but it wasn't enough to help Australia beyond 3-137 thanks to a tricky wicket, and outstanding Sri Lankan bowling.
Lasith Malinga might not have picked up a wicket, but was tremendous with 0-19 from his four overs. Kulasekara finished with 1-21 and Ajantha Mendis 0-26. All Sri Lankan bowlers aside from Mathews (0-39) kept things nice and quiet.
The wicket clearly wasn’t easy to score on, but Warner did show it was possible and Sri Lanka made a lightning start to its run chase largely thanks to Kusal Perera.
Veteran Tillakaratne Dilshan was offering good support despite copping a nasty blow to his head from a Ben Laughlin bounce. That opened up a nasty cut above his eye, but he continued on before falling for 16 off Xavier Doherty when Laughlin took an outstanding running and diving catch.
Sri Lanka then also lost Kusal Perera (33 from 22), Mahela Jayawardene (8 from 10) and Dinesh Chandimal (5 from 6) in quick succession to be in a little bit of bother at 4-69, but Lahiru Thirimanne first offered good support to Mathews making 20 from 15 balls.
He fell with the score 5-104 and from there Mathews and Thisara Perera comfortably took Sri Lanka to victory.
Doherty finished with 2-21 from four overs for Australia with Mitchell Starc taking 1-19 and Glenn Maxwell 2-15. Laughlin had a horror night besides his terrific catch, though, ending with 0-46 from 3.5 overs.
Australian captain Bailey thought that the way his side defended a small total was the most disappointing aspect of the night.
"Our fielding was disappointing and probably cost us 10 runs and that adds up," Bailey said.
"I thought Sri Lanka bowled unbelievably well their last four overs. Any side that can bowl to Davey set and deprive him of boundaries ... they executed unbelievably well."
Mathews enjoyed his first win as Sri Lankan captain and felt his side did all the little things right in the field and praised Malinga and Kulasekara - who allowed just 14 runs in the final two overs - as the difference.
"We started brilliantly, we were electric in the field and the bowlers bowled extremely well," Mathews said.
"Lasith and Kulasekara were the ones who pulled us back."
The second and final match of the series will now take place at the MCG on Monday before Australia turns its attention to the West Indies.