The deaths occurred in the cities of Guaruja, Santos and Sao Vicente of Sao Paulo state, according to a statement from its civil defense office. One person in the area remained missing.
Brazil's southeast region has been punished by heavy rains this year, causing recurrent floods and landslides. The worst instance came in January, when dozens perished in landslides in the interior state of Minas Gerais.
Some parts of Rio de Janeiro were flooded on Sunday and Monday, and several people died, according to local firefighters. Further, state authorities said in a statement more than 5,000 people had been forced from their homes.
Residents are growing frustrated, and one threw mud at Rio's Mayor Marcelo Crivella's head as he spoke to reporters on Monday.
Moderate to strong rain was expected to continue Tuesday along Sao Paulo's coast, according to the civil defense office.