The 41-year-old, who spent 17 years with the Italian club before leaving for PSG last summer, has signed a one-year contract.
He underwent a medical in Turin on Thursday morning.
“After a year away from Turin, Gianluigi Buffon has returned to Juventus after penning a one-year contract which will tie him to the club until 30 June 2020. Buffon is back home!”