Sydney
Police superintendent Phil Rogerson says there were no arrests and that it was one of the biggest protests in Australian history.
"Obviously there was large protests back at the Vietnam era, but over the last 10 years we haven't seen any protests this size," he said.
People of all ages, race and persuasion gathered to take part in the anti-war walk.
Banners, placards and T-shirts all carried the same message - a peaceful resolution to the crisis
Addressing the rally, New South Wales Labor Council secretary John Robertson condemned the so-called "coalition of the willing" put together by US President George W Bush.
"It's willing to plunge the world into war, it's willing to ignore the UN, it's willing to kill innocent men, women and children, in Iraq, and it's willing to play the politics of propaganda and confusion and we will not accept that sort of coalition of the willing," he said.