More than 100,000 turned out for the funeral Mass, lining the streets of Recife as the coffin made its way through the city.
Campos, 49, died with six others when his plane, on its way to a campaign stop, crashed in a residential neighborhood of the city of Santos, near Sao Paulo. Several people on the ground were also injured.
At the time of his death, Campos was polling in third place with about 10 percent of voters' preferences, behind incumbent President Dilma Rousseff of the Workers' Party with 36 percent, and center-right Social Democracy Party candidate Aecio Neves with 20 percent.
Campos' running mate, former Environmental Minister Marina Silva, is expected to run in his place. Although Silva has declined to confirm whether she will run, she told reporters at the funeral on Saturday "I have a responsibility and commitment."
Presidential elections will be held on October 5.