A middle-order collapse from Sri Lanka and David Warner's brilliant century ensured Australia completed a 4-1 series victory thanks to a comprehensive five-wicket win in Sunday's one-day international.

Sri Lanka, who trailed by an unassailable 3-1 deficit heading into the final Pallekele contest, crumbled from 73-0 to 195 all out.

Mitchell Starc claimed 3-40 and his tally of 12 wickets is his most in a bilateral series, while spinners Travis Head (2-22) and Adam Zampa (2-43) made key contributions.

Warner then took centre stage with the highest ODI score by an Australian in Sri Lanka, aided brilliantly by George Bailey in a fantastic 132-run stand. 

Stand-in skipper Warner accelerated after passing 50 and the opener's mature knock of 106 included nine fours and came from 126 deliveries.

It was a decent enough start for Sri Lanka, who earned a 3-0 whitewash in the Test series, as Dhananjaya de Silva (34) and Danushka Gunathilaka (39) put on 73 for the opening wicket.

The wheels quickly came off, though, as three wickets went for five runs. De Silva mishit a James Faulkner ball to mid-on in the 14th over and six balls later Gunathilaka had his leg stump taken up by Zampa.

Dinesh Chandimal (1) then became Starc's first victim and the wickets continued to tumble, Head leaving Upul Tharanga (15) and Kusal Perera (14) in a spin before Dasun Shanaka (13) fell to Zampa.

Sachith Pathirana added 32, but that was Sri Lanka's only resistance as Starc returned to help sweep up the tail.

Australia made an edgy start in reply as Matthew Wade (3) gloved Dilruwan Perera behind and was given out on review, before Usman Khawaja (6) top edged the same man to Gunathilaka at cover point.

Warner ensured the scoreboard ticked over with sensible singles and measured strokes and it took 72 balls for his half-century to arrive in the 24th over.

But he shifted through the gears from there, ending the same over with two boundaries and he continued to regularly find the ropes.

Bailey was trapped lbw by Dilruwan Perera on 44 but he had proved a fine foil for Warner, whose century arrived with a single off De Silva in the 35th over.

Frustratingly for Warner he half-volleyed a lollipop delivery straight back to De Silva in the closing stages, but the damage had already been done.