Foz do Iguaçu is the closest city to Iguazú Falls National Park on the Brazilian side. In order to visit both sides, you will need to cross the border between Argentina and Brazil.
Buses connect Foz do Iguazú to both sides of the falls, and you can also book a private transfer.
This 7-day itinerary gives you a chance to see both sides of the falls and also explore Buenos Aires. If you have a bit more time, this 12-day itinerary takes you south to see the Perito Moreno Glacier and Tierra del Fuego, and then back up to Iguazú Falls.
By Private Transfer
Duration: 15 minutes to the Brazilian side, 30 minutes to the Argentine side
It's possible to book private transfers to both sides of the falls from Foz do Iguazú, which can also pick you up directly from your hotel and take you to the entrance of the park. Some also offer transfers directly from Foz do Iguaçu Airport (IGU). Don't forget to bring your passport in order to cross the border.
Duration: 35 minutes to the Brazilian side, 2 hours to the Argentine side
Buses leave Foz do Iguaçu every 20 minutes and stop at the Brazilian side of the falls first. To reach the Argentine side of the falls, you'll need to change buses once at the Brazilian falls and take a bus to Puerto Iguazú's bus terminal, where you can switch buses again and catch one that will take you to the Argentine side.