The east wing of the Grand Lisboa Palace, owned by SJM Holdings, and the Grand Hyatt Hotel, owned by Melco Resorts, will together offer nearly 800 rooms, they said.
The Sheraton Hotel in Sands China and the Londoner Resort have already been used as quarantine facilities.
The announcement comes as Macau reported 128 new cases on Thursday, bringing the total to 1,215 cases since mid-June. More than 15,000 people are in quarantine, authorities said.
The former Portuguese colony has only one public hospital for its more than 600,000 residents, and its medical system was already under strain before the coronavirus outbreak.
Authorities have set up a makeshift hospital in a sports dome near the city’s Las Vegas-like Cotai Strip, and are attended by around 600 medical workers from the mainland.
Macao adheres to China’s “zero COVID” policy which seeks to stem all epidemics at almost any cost, against the global trend of trying to coexist with the virus.
Although the government has not imposed the kind of city-wide lockdown seen in mainland Chinese cities, Macau is effectively locked down and most facilities are closed. Residents have been told to stay home and restaurants only offer take-out.
Residents flocked to food markets and grocery stores on Thursday, fearful that the city would be shut down entirely. The government denied the rumors and urged the public not to panic and hoard food, according to local broadcaster TDM.
Hong Kong, the neighboring global financial hub, has experienced similar chaos after lockdown rumors surfaced on several occasions. Authorities never imposed a full lockdown and began easing COVID restrictions, even as the number of cases reached around 3,000 a day.