Djokovic, who is Serbian, is the fourth player who participated in matches last week in Belgrade, Serbia's capital and largest city, and in Zadar, Croatia, over the weekend to test positive for COVID-19.
Djokovic's wife also tested positive.
"The moment we arrived in Belgrade we went to be tested. My result is positive, just as Jelena's, while the results of our children are negative," he said in a statement.
The number of cases and death toll from the coronavirus in Croatia and Serbia have been relatively low, with more than 2,000 cases and 107 deaths being recording in Croatia and more than 12,000 cases and 262 deaths in Serbia.
Djokovic was criticized for bringing in other players from around the world for the tournament.