The Sri Lankans, seeking 188 for victory, were bowled out for 146 in 18 overs — but they still win the three-game series 2-1.
Their chase was given early impetus by Dilshan Munaweera, who smacked 37 from 25 balls before 19,326 spectators at Adelaide Oval.
But from 0-41 in the fourth over, the tourists lost traction and slid to 4-76 in the 10th.
Australian captain Aaron Finch, who earlier cracked a half-century — as did his opening partner Michael Klinger — used constant bowling changes to unsettle Sri Lanka.
Finch deployed seven different bowlers in the initial 10 overs and four of them had wickets by the midpoint.
From then, Sri Lanka perished in a do-or-die mission with only Milinda Siriwardana (35 from 27 balls) offering resistance. (Courtesy ABC)