Three females named Zala, Nima and Run Run and Kiumbe, a male, were tested after keepers noticed they showed slight symptoms of coronavirus.
Two staff at the zoo also tested positive for coronavirus, the authorities said, after the outbreak was first detected last month.
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Authorities are investigating how the lions became infected.
Keepers carried out PCR tests on the lions in the same way as humans are tested as the animals are accustomed to contact with the zoo staff.
The Veterinary Service of Barcelona contacted colleagues at the Bronx Zoo in New York, where four tigers and three lions tested positive for Covid-19 in April. It is the only other zoo where large felines are known to have contracted coronavirus. All recovered.
"The Zoo has contacted and collaborated with international experts such as the Veterinary Service of the Bronx Zoo, the only one that has documented cases of Sars-CoV-2 infection in felines," the Barcelona zoo said in a statement.
"The lions were given veterinary care for their mild clinical condition - similar to a very mild flu condition - through anti-inflammatory treatment and close monitoring, and the animals responded well."
The four-year-old male and the females, who are all 16 years old, have had no contact with other animals at the zoo, which is open to visitors.