Hossein Karroubi said his father, who ran against and lost to Mahmoud Ahmadinejad in the June 2009 election, returned to his home in a northern Tehran district Saturday night.
Mehdi Karroubi has been given access to the Islamic Republic of Iran Broadcasting (IRIB) channels, his son said.
Hossein said his father and mother are staying together and the rest of the family can regularly visit their parents as before.
Mehdi Karroubi is accused of inciting unrest following the vote which saw the reelection of Ahmadinejad.