Three females named Zala, Nima, and Run Run and one male called Kiumbe were tested after displaying mild symptoms.
Two staff members also tested positive for the virus, the zoo said.
An investigation is underway to establish how the animals became infected, but it is thought they may have been in contact with an asymptomatic member of staff.
Zookeepers reportedly carried out a standard PCR swab test on the four lions – the same method used on humans – because they are comfortable having close contact with staff.
The animals had been showing upper respiratory symptoms, according to an earlier statement from the zoo. Most symptoms have disappeared other than minor coughing and sneezing.
They are being treated with anti-inflammatory drugs and monitored closely. “The lions were given veterinary care for their mild clinical condition – similar to a very mild flu condition – and [they] responded well,” a statement said.
Some of the famous zoo’s animals have begun to notice the lack of visitors
It is only the second known case in which large felines have contracted coronavirus.
Staff at Barcelona Zoo contacted colleagues at the Bronx Zoo in the US, where the first known case was recorded in April when four tigers and three lions tested positive for coronavirus.
One of the tigers, Nadia, is believed to be the first known case of an animal becoming infected with Covid-19 in the US.
All of the animals at the Bronx Zoo made a full recovery.
The risk of infection between zoo animals and visitors, meanwhile, is low becoming of a lack of proximity. “Simply, no one who comes to see [the lions] gets close enough,” the Barcelona Zoo statement said.