Djokovic, along with Grigor Dimitrov, Borna Coric and Viktor Troicki, tested positive after playing in the Adria Tour, an exhibition tournament organised by the 17-times Grand Slam champion.
The tournament witnessed packed stands during the opening leg staged at Djokovic's tennis complex in Belgrade from June 13-14, with players hugging at the net, playing basketball, posing for pictures and attending press conferences together.
The second leg was held in Zadar from June 20-21.
The players did not break any Serbian or Croatian government protocols, as neither country required the athletes to maintain any social distancing
However, Djokovic, who was heavily criticised for staging the event, issued an apology, saying he was extremely sorry for the harm that had been caused.