Thousands of people protested in the capital, Brasilia, as well as 43 other cities, according to Brazilian broadcaster Globo.
Demonstrators chanted and beat drums, demanding more economic support and vaccines.
"We are protesting against the genocidal Bolsonaro government that did not buy vaccines and has done nothing to take care of its people in the last year," Aline Rabelo, a 36-year-old protesting in Brasilia, told Reuters news agency.
Bolsonaro has been widely criticized for not taking up early offers to buy coronavirus vaccines. To date, only 11% of Brazil's population is fully vaccinated while 29% have received a first dose, according to the Health Ministry.