In his absence, Juve have won just one of their four matches in all competitions, and they lost 2-0 at home to Barcelona in the Champions League in midweek.
"Cristiano Ronaldo carried out a check with a diagnostic test [swab] for COVID-19," a club statement read.
"The exam provided a negative result. The player has, therefore, recovered after 19 days and is no longer subjected to home isolation."
Ronaldo, 35, missed out on the chance to participate in the highly anticipated clash with Barca's Lionel Messi on Wednesday, and without him, Juventus succumbed to defeat.
In the league, they have suffered back-to-back draws -- against Crotone and Verona -- with their only victory coming away to Dynamo Kiev in the Champions League. Their next match is at Spezia on Sunday.
Ronaldo tested positive for the coronavirus on Oct. 13 while on international duty with Portugal, which later led Italian sports minister Vincenzo Spadafora to claim the ex-Real Madrid forward had breached protocol. Ronaldo denied the allegation.