Sri Lanka elected to bat first after winning the toss against Australia.
Travis Head, Josh Inglis and Glenn Maxwell will add considerable batting firepower for Australia in their final match before the Champions Trophy starts next week. Quick Ben Dwarshuis and legspinner Tanveer Sangha were also included for the second ODI in Colombo, with Cooper Connolly, Alex Carey, Marnus Labuschagne, Nathan Ellis and Spencer Johnson making way.
Jake Fraser-McGurk shifted down to No.3 with Head to open alongside Matthew Short, while allrounder Aaron Hardie moved up to No.6 and Maxwell was listed at seven.
Sri Lanka skipper Charith Asalanka once again won the toss and elected to bat on a dry surface in the series-finale. Sri Lanka claimed the opener with a 49-run victory at the same venue after Asalanka engineered a remarkable turnaround with an extraordinary century.
Sri Lanka continued their strong ODI form and have won eight of their past 12 matches in the format, but won't be part of the Champions Trophy.
Asalanka hoped for an improved batting performance in this match and their only change was Nishan Madushka replacing Avishka Fernando at the top of the order.
Australia were considerably weakened for this series and the subsequent Champions Trophy. They are without Pat Cummins, Josh Hazlewood, Mitchell Starc, Mitchell Marsh and Marcus Stoinis for various reasons.
Sunny and humid conditions were expected through the day fixture.
Sri Lanka: Pathum Nissanka, Nishan Madushka, Kusal Mendis (wk), Kamindu Mendis, Charith Asalanka (capt), Janith Liyanage, Dunith Wellalage, Wanindu Hasaranga, Maheesh Theekshana, Eshan Malinga, Asitha Fernando
Australia: Travis Head, Matt Short, Jake Fraser-McGurk, Steve Smith (capt), Josh Inglis (wk), Aaron Hardie, Glenn Maxwell, Sean Abbott, Ben Dwarshuis, Adam Zampa, Tanveer Sangha