Jair Bolsonaro appeared on a live broadcast where he laughed as he told viewers he had “mold” in his lungs.
He explained that he was taking antibiotics for the infection, which left him weak.
He said, “I just had a blood test. I felt a little weak yesterday. They also found a bit of infection.
“Now I am on antibiotics. ”
Mr Bolsonaro added: “After 20 days indoors, I have other problems. I have mold in my lungs. ”
He spent nearly three weeks in isolation at the Presidential Palace after being diagnosed with the coronavirus July 7.
He tested negative for the virus last Saturday, but his wife Michelle, 38, tested positive on Thursday.
Mr Bolsonaro, 65, gave no further details about his infection.
Even after being infected, the Brazilian president downplayed the severity of the virus.
He has consistently said that restrictions on businesses would be more damaging than the disease, but most Brazilians disagree with his approach, according to recent opinion polls.
Meanwhile, Brazilian Science and Technology Minister Marcos Pontes, 57, has become the latest politician and the fifth cabinet minister to announce he has the coronavirus.
On Thursday evening, the Brazilian Ministry of Health confirmed a total of 2,610,102 cases of coronavirus, against 2,552,265 the day before.
Some 91,263 people have died nationwide after testing positive for the disease.