An estimated 50,000 people flooded the city's central Cathedral Square for the second night running, marching through streets and waving banners carrying slogans such as, "The people have awakened."
One group tried to break into the mayor's office, The New York Times reported.
Some people among the demonstrators smashed windows, ransacked stores and set fires.
People were seen carrying appliances from looted stores, the newspaper Folha de Sao Paulo reported.
Overnight demonstrations were also reported in at least two other cities.
Monday night demonstrations in at least a dozen cities drew a quarter-million people onto the streets.
Demonstrators say they're angry about political corruption, the high cost of living and huge public spending for the 2014 FIFA World Cup soccer tournament and the 2016 Olympic Games and Paralympic Games.
They say Brazil's leaders are spending hundreds of millions of dollars to cultivate the country's global image, but they're letting basic services such as education and healthcare languish.
President Dilma Rousseff, a former guerrilla imprisoned under Brazil's dictatorship that ended in 1985, sought to appease protesters.
"These voices, which go beyond traditional mechanisms, political parties and the media itself, need to be heard," said Rousseff, who faces re-election next year.
"The greatness of yesterday's demonstrations were proof of the energy of our democracy," she said.
Brazil's demonstrations began with anger over an increase in bus and subway fares. But as with many other protest movements, they mushroomed into a broader expression of anger at the government.
Politicians in several cities said late Tuesday they would cut or consider reducing the fares.