WhatsApp was temporarily suspended in Brazil after a judge said the company had failed to hand over information requested in a criminal investigation.
The third suspension in two years lasted for a few hours, affecting millions of users.
But Supreme Court judge Ricardo Lewandowski later lifted the nationwide blockage, saying it was disproportionate.
WhatsApp said they did not have access to the details requested.
The most recent suspension happened in May, and forced 100 million people to turn to alternative services – a huge proportion of the internet-using population in a country with some of the world’s highest mobile phone charges.