Germany won gold in the highly anticipated canoe sprint event in 3:43.912, nearly a full second ahead of the Brazilian boat, while Ukraine took bronze.
The victory marked German paddler Sebastian Brendel's second gold of the Games, this time alongside partner Jan Vandrey. Brendel took gold in the men's C-1 1000 metres on Tuesday, successfully defending his Olympic title in the event.
Queiroz dos Santos previously won silver and bronze in the men's C-1 1000 metres and men's C-2 200 metres respectively, but missed out on gold despite setting the pace early on with a typically fast start.
Hungary's Kozak paddles her way to a triple gold
Charming home-country crowds since his debut at the Rodrigo de Freitas Lagoon, Dos Santos is Brazil's first-ever Olympic medallist in canoe sprint.
Dos Santos and team mate Erlon de Souza Silva led for much of the race to wild applause from the crowd, who chanted:
Brazil! Brazil! Brazil!
Onlookers outside the venue crowded the sidewalk and peered across the lagoon to watch as the Brazilian pair stormed out of the blocks, but Germany overtook the field only in the last moments, claiming first place in the home stretch.
Great Britain's Liam Heath sprints to gold in the 200m kayak
GB's Heath and Schofield secure dramatic silver in 200m kayak final