The cats, from separate areas of New York state, had mild respiratory illness and are expected to make a full recovery. It is believed that they contracted the virus from people in their households or neighbourhoods, according to the US Centers for Disease Control and Prevention (CDC).
"Animals, pets, can get infected. There's no evidence that the virus is transmitted from the pet to a human," Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said at the daily coronavirus briefing.
There are few known Covid-19 infections of pets globally.
According to the American Veterinary Medical Association, one cat in Hong Kong tested positive without displaying symptoms, while a cat in Belgium recovered nine days after falling ill.
Five tigers and three lions at the Bronx Zoo in New York have also tested positive for Covid-19, including one tiger who never developed a cough, according to the Wildlife Conservation Society, the non-profit which runs the zoo.
"Our cats were infected by a staff person who was asymptomatically infected with the virus or before that person developed symptoms," the WCS said on Wednesday local time.
"All eight cats continue to do well. They are behaving normally, eating well, and their coughing is greatly reduced."
None of the zoo's leopards, cheetahs, puma or serval were showing any signs of illness, it added.
New York City is the epicentre of the coronavirus outbreak in the US, which like much of the world is taking extraordinary measures to prevent the spread, but authorities indicated owners did not need to fear their pets.
"There is no evidence that pets play a role in spreading the virus in the United States," the CDC said in a statement.
"Therefore, there is no justification in taking measures against companion animals that may compromise their welfare. Further studies are needed to understand if and how different animals, including pets, could be affected."
The agency recommends that owners not let their pets interact with people or other animals outside the household. Cats should be kept indoors and dogs should be walked on a leash, maintaining at least six feet (1.8m) from other animals and people, it said.