Does it need a visa entre even for a day to visit Brazilian side of Iguazu Fall?
Yes you do.
They are pretty hardcore about it as well. If you do get a visa. At your entry point into Brazil you will get a piece of paper that you will need to make declarations that you are not carrying "bad" things. Make sure you keep this with your passport.
Basically it is Australia's fault because Brazil has a reciprocity policy with visa. As Australia requires Brazilians to have a visa for any length of time then Brazil requires the same for Australians. about 7 years ago
Yes you do need a visa though annoyingly, mine was never checked (took a taxi from Argentina side and was simply waved through) when I went there a few years ago. That isn't worth the risk as most seem to get checked as described above. Get the correct paperwork as the falls are simply stunning (and it is a long way to travel from Australia to get there) and you'd miss a lot by not going to the Brazilian side of the falls. about 7 years ago