The New Orleans Pelicans announced the rookie forward had arrived back in Orlando after leaving to attend what the team called "an urgent family matter" on July 16.
Williamson underwent daily coronavirus tests and produced negative results throughout; he immediately went into a quarantine period before he can join up again with his teammates ahead of a resumption in the season.
"My family and I appreciate the love and respect that everyone showed us while we dealt with a private family matter," said Williamson in a statement.
"I'm excited to rejoin my team in Orlando and look forward to getting back on the court with my teammates after quarantine."
Provided the 20-year-old remains negative for COVID-19, Williamson could be cleared to play in New Orleans' first scheduled game of the NBA's restart, against the Utah Jazz on July 30.
The 2019 first overall draft pick was averaging 23.6 points and 6.8 rebounds when the season was halted due to the global pandemic, having missed the first 44 games while recovering from arthroscopic surgery on his right knee.
New Orleans enter the restart in 10th place in the West.