Ahmadinejad said last year he would put up the car for auction and donate the money to a housing project for low-income families. A multilingual website was designed to take the bids.
"President Ahmadinejad's Peugeot 504 was sold for 2.5 billion tomans ($2.5 million) to an Iranian who took part in the auction," ISNA news agency reported.
"After Iran, most visitors of the website were from America," noted the head of Iran's Welfare Organization at a ceremony to hand the car key to its new owner.
ISNA's report didn't identify the buyer, but quoted the individual's lawyer, Mamoud Isari, as saying the buyer plans to build a museum and exhibit the car.
The 34-year-old white sedan was put up for auction in January in a move by the president to appear to fulfil a campaign promise to put a roof over the head of every Iranian.
Ahmadinejad made a point of being seen in the sedan when he was Tehran mayor. He has rarely used the car since becoming president in 2005.
The car would normally be worth around $2,000 on the local market.