After dismissing Sri Lanka for a lowly 76, the Southern Stars were cruising at 1 for 45 before the slump set in.
Captain Meg Lanning was the first to go for 27, before star all-rounder Ellyse Perry was out for 4, vice-captain Alex Blackwell a first-ball duck and Nicole Bolton 19 to leave the Southern Stars reeling at 5 for 50.
But Jess Jonassen (12), Alyssa Healy (12 not out) and Erin Osborne (4 not out) steered the ship home, as the Southern Stars claimed a four-wicket win in the first of four one-day internationals with 34.2 overs to spare.
Earlier, opening bowler Holly Ferling (3 for 4) and Megan Schutt (2 for 5) ripped through the Sri Lankan top order, with five of their top six failing to trouble the scorers and the other, Imalka Mendis, scoring just 1.
Spinners Kristen Beams (3 for 16) and Erin Osborne (2 for 24) then finished the job inside 25 overs.
“They’re really good here, great conditions for spinners,” Beams said.
“Just to have a tiny bit in the wicket gives you something. I asked our assistant coach how I could get a passport.”
The series returns to Dambulla for the second match on Tuesday. (Courtesy AAP)