The company and country are engaged in an ongoing fight over whether Brazilian officials should be able to read the messages of users of the service. Brazil has argued that it is important for security, but WhatsApp says that it is impossible to share the data,which is fully encrypted and therefore can only be read by the sender and recipient.
That has led to the roughly 100 million people who use WhatsApp in Brazil finding themselves unable to send or receive messages.
The outage came as the result of a judgement by Marcel Maia Montalvao, a judge in the small, remote northeastern state of Sergipe, who ordered the suspension.
The fight over data has been happening for months. In March, Facebook’s most senior staff member in Latin America was detained and held as officials accused it of withholding information that was important for drug trafficking and organised crime investigations.
At the time, a spokeswoman for federal police in Sergipe, Monica Horta, said investigators had requested content from a WhatsApp messaging group as well as other data, including geolocation. Investigators first contacted WhatsApp several months earlier but hadn't received a response, Horta said.
In a statement widely cited in Brazilian media, WhatsApp said the company was disappointed by the judge's decision, saying it "punished more than 100 million Brazilians who depend on our service."
The statement also said it does not have the information that authorities are demanding in the case. WhatsApp has been rolling out a so-called end-to-end encryption system under which only the sender and recipient can access the content of messages.
Brazilian authorities also clashed with Facebook in December, when a judicial order forced telecoms to block WhatsApp for about 12 hours over its alleged refusal to cooperate with a police inquiry.
Facebook CEO Mark Zuckerberg at the time said he was "stunned" by the "extreme decision."
The website for the Sergipe state's court system was also down Monday.