Still smarting over their team's humiliating World Cup elimination, many Brazilians are backing Germany over their South American neighbours, but football arch-rivals, in the game at the iconic Maracanã Stadium.
Some 100,000 Argentinians are expected to descend on Rio.
Since the tournament kicked off on June 12, legions of Argentines have flooded Brazilian cities, taunting their hosts with chants that their hero Diego Maradona was better than Brazil legend Pele.
After Brazil lost 7:1 to Germany in the semi-final, Argentines held up seven fingers and chanted "They ate seven goals!" Brazilians chanted back that they had won a record five titles.
After Brazil lost 3:0 to the Netherlands in Saturday's third-place playoff, taking the two-game tally to 10 goals, a group of Argentines walked down a Rio street in the dead of night and loudly counted to 10.
Cars and buses packed with Argentine fans waving their country's white and blue flag and honking their horns streamed across Rio streets hours before the final. For Brazilians, seeing Argentina
win on their soil would add insult to injury.
"We're in a tough spot. We have the choice between our executioners (Germany) or our historic rivals, the Argentines," said Francisco Silva, a public worker. "I'm choosing Germany because if the 'hermanos' (brothers) win, they'll mock us for life."
Silva was taking the subway near the Sambadrome, the open-air venue of the Carnival that the city opened for the countless Argentine motorhomes, buses and cars that have arrived.