About 800 demonstrators demanded the Australian government put pressure on Colombo to declare a permanent ceasefire in its campaign against Tamil Tiger rebels.
Spokeswoman Sam Pari said the protesters also wanted Australians to boycott Sri Lankan goods.
"Every dollar you spend that reaches Sri Lanka is being used to buy bombs and bullets which have killed over 6,500 Tamil civilians in the last 3 months," she said.
Australia's Tamil community has staged a number of protests as the Sri Lankan military closes in on the remnants of the Tamil Tigers in a shrinking sliver of land on the north of the island.
Action from the protesters has included a hunger strike earlier this month that was called off when two men were hospitalised with dehydration.
At the time, Australian authorities told the hunger strikers that their demands had been heard, but Pari said they had done nothing since.
"The Australian government assured us more than a week ago that they would take action