"It began with some indisposition on Sunday and worsened on Monday, with fatigue, fever, and muscle pain," Bolsonaro explained.
Nevertheless, the president still considers that attention given to the pandemic in Brazil is exaggerated, even though the South American nation has become one of the world's disease hotspots due to his policies.
Bolsonaro plays down social distancing and has recently vetoed the obligatory use of masks in shops, churches and schools in Brazil.
There was no social distancing even when he announced having tested positive for Covid-19: pic.twitter.com/oFSRTbScrG
The Brazilian president had tested negative on three previous occasions, after meeting with U.S. President Donald Trump in March.
Also, Bolsonaro, who has called COVID-19 a "minor flu" in the past, keeps on defending the use of hydroxychloroquine, a drug whose effectiveness has caused controversy among medical authorities.