The vibes remained upbeat among the thousands of fans on Friday, despite several people being evicted following a small brawl at Melbourne's Federation Square, which had reached capacity by 10am.
Fans, mostly teenage boys dressed in a sea of green and gold, began gathering rapidly ahead of Australia's match against Paraguay, which kicked off at noon.
It is unclear whether planned intensive security checks were able to happen as the crowd streamed through the entrance.
Two flares have made it through security, with fans cheering as they were let off.
Just after 10am, fans were told to make their way to nearby AAMI Park as Federation Square had reached capacity.
Inside, soccer fans young and old, mostly teenagers who should be at school for the last day of term, gathered to experience the "atmosphere" of watching with a crowd.
The teens, wearing a mixture of green and gold, black tracksuits and some wearing the Australian flag as a cape, were relatively well behaved, cheering and chanting as others bounced beach balls around the crowd.
Chants of "Aussie, Aussie, Aussie" could be heard through the crowd.
Year 10 students Adrian, Jaxon, Ben and Xavier said they skipped school so they could be a part of the day, something their parents weren't aware of.
Another group of teens Atticus, Milla and Jonah said they had come to Federation Square with their parents' blessing given it was the last day of school term, and said they couldn't wait to cheer the Aussies home.
There was a noticeable police presence, with many officers wearing protective sunglasses and black helmets, watching the crowd from a distance.
Elsewhere, Tumbalong Park in Sydney's Darling Harbour is the city's flagship live site while Brisbane-based Socceroos faithful gathered at South Bank and those in Perth watched at Northbridge Piazza.
With a win or draw at Levi's Stadium in Santa Clara, Australia will finish second in group D, and face the Group G runners-up - one of Belgium, Egypt, Iran or New Zealand - in Dallas.
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