The 35-year-old featured in Portugal’s two Nations league games against Spain and France, and was preparing for a third against Sweden on Wednesday.
Ronaldo is said to be asymptomatic and is currently observing self-isolation.
Tests conducted on other teammates returned negative.
Statement from the Portuguese Football Federation read in part:
"Cristiano Ronaldo was released from the squad of the National Team after a positive test for COVID-19, so he will not face Sweden.
"The Portuguese international is doing well, without symptoms, and in isolation.
"Following the positive case, the remaining players underwent new tests this Tuesday morning, all with a negative result, and are available to Fernando Santos for training this afternoon.’