"Customs, literally . . ." Top 5 Page for this destination Parque Nacional del Iguazù Local Custom Tip by acemj

If you will be crossing borders, keep in mind you may need a Visa (especially going into Brazil). Even if you are only planning to visit the Brazilian side of the falls, you'll still need a Visa if your country requires Brazilians to get a Visa to visit. They are big on the concept of reciprocity.

When crossing the borders, the buses will stop and everyone has to get out and walk through customs. The customs officer will ask you one or two short question, give you a stamp and wave you through. Then you just get back on the bus (or taxi) and proceed on your way.