The Portugal forward had been self-isolating since testing positive for the virus while away on international duty in early October.
Ronaldo has not played for Juve since a 2-2 draw against Roma at the end of September, and this week missed a reunion with Barcelona adversary Lionel Messi in the Champions League.
A statement from Juventus said: "Cristiano Ronaldo carried out the check with a diagnostic test (swab) for COVID-19.
"The examination gave a negative result. The player is therefore cured after 19 days and is no longer subjected to home isolation."