Australia's early batting momentum in the third triangular series final was spoiled by a diligent Sri Lankan effort, the hosts slipping to 4 for 125 after 25 overs at Adelaide Oval.
Matthew Wade and David Warner had given Australia a strong start with a stand of 75 at better than five runs an over, before Warner edged behind.
Shane Watson hinted at a strong innings but threw his hand away on 19, swinging an outfield catch, Michael Hussey was run-out, and Wade's subsequent dismissal added to Sri Lanka's renewed sense of control.
As he had done in the second final, Tillakaratne Dilshan took the new ball and bowled his overs with thrift and direction.
Farveez Maharoof and Rangana Herath took three wickets to send the Aussie batting line up back to the dressing room.
However, Clint McKay and Brett Lee made valuable contributions of to take the Australians to a score of 231 runs at the end of their allotted 50 overs.