Mahela struck a 66-ball 50 studded with five boundary hits while Dilshan made a workmanlike 62 inclusive of three boundaries.
The duo knitted a fine 64-run stand for the fifth wicket to steady tottering Lankan ship after the much-vaunted Aussie new-ball bowlers ran thro' the top-order. The 50-run stand between Dilshan and Chamara Silva (35) for the sixth wicket also helped Lankans cause.
In-form Aussie seamer Bracken plucked 4/29 from his 10 overs after conceding just nine runs from a miserly eight-over opening spell.
After winning the toss, Lankan top order stumbled against the probing Aussie new-ball bowlers. The Islanders stumbled to 91/4 at the 25-over mark.
Opener Dilruwan Perera made just five before being trapped in front by a Brett Lee yorker which straightened late.
Sanath Jayasuriya, in almost certainly his last international on Australian soil, gave the 20,000 or so fans present glimpses of his old form.
The 38-year-old, who helped transform the way teams approached the first 15 overs of one-day matches, carved Lee for 10 runs in two consecutive balls, including a six where he was caught over the rope.
But he bowed out for 23 when caught at slip after prodding at one just outside off from Nathan Bracken, whose opening eight-over spell yielded three maidens and the frugal figures of 9/1.
The Lankans slipped further into the mire when Sangakkara was also brilliantly caught at slip by Hussey, who won a berth in the cordon in the absence of Matthew Hayden.
Their best batsman in Hobart, Chamara Kapugedera couldn't take his form across Bass Strait, making just two from 23 balls before edging James Hopes to Adam Gilchrist, who is playing his final match at the MCG.
Mahela and Dilshan then held their ground firm and batted sensibly milking the ball in the gaps at the huge MCG for singles and twos interspersed with odd boundaries. The duo was at ease with pace but struggled against Hogg and Hopes. Hogg accounted for Mahela while Dilshan failed to beat the throw from Hopes.
Lanka 221 all out in 50 overs (Dilshan 62, Mahela 50, Chamara 35, Jayasuriya 23; Bracken 4 for 29, Lee 2 for 55) Vs Australia.