The tiger, a 4-year-old female Malayan tiger named Nadia, developed a dry cough and a decrease in appetite. She was tested out of an abundance of caution, and the results were confirmed by the USDA's National Veterinary Services Laboratory in Iowa, the society said.
Her sister Azul, two Amur tigers and three African lions also showed coronavirus symptoms, but all of the cats, including Nadia, are expected to recover.
The zoo said the cats were infected by a person caring for them who had COVID-19 but was asymptomatic or had not yet developed symptoms.
"Appropriate preventive measures are now in place for all staff who are caring for them, and the other cats in our four WCS zoos, to prevent further exposure of any other of our zoo cats," the Wildlife Conservation Society, the parent company of the Bronx Zoo, said in a statement.
It is unknown how the disease develops in big cats. There is also no evidence that animals can infect people with the virus.
Nadia and Azul became visitor favorites after their appearance on Animal Planet's 2017 docu-series "The Zoo."
The rare Malayan tiger siblings were born at the zoo in 2016 but needed to be hand-raised after their mother rejected care.
Many people asked how the tiger was able to get tested for COVID-19 when it's still difficult for people.
Dr. Paul Calle, Bronx Zoo Chief Veterinarian said, "The COVID-19 testing that was performed on our Malayan tiger Nadia was performed in a veterinary school laboratory and is not the same test as is used for people. You cannot send human samples to the veterinary laboratory, and you cannot send animal tests to the human laboratories, so there is no competition for testing between these very different situations."
The Bronx Zoo has been temporarily closed since March 16.