Photographer Francois-Marie Banier and his partner Martin d'Orgeval were charged in the city of Bordeaux and released on bail, their lawyers said.
The two denied the charge and said any financial benefits they obtained from their relationship with Bettencourt were given of her own free will, the lawyers, Pierre Cornut-Gentille and Jean-Alain Michel, said.
Bettencourt, France's richest woman, was placed under the guardianship of family members in October amid reports her mental health at 89 is declining.
The guardianship ended a long legal battle over her vast fortune, estimated to be worth more than €16 billion ($21 billion).
The family, including estranged daughter Francoise Bettencourt-Meyers, had long accused Banier of taking advantage of the heiress.
Banier was named a beneficiary in Bettencourt's will drawn up in December 2007. But Bettencourt broke with Banier earlier this year, cutting him out of her will and depriving him of an estimated €1.25 billion.
Dubbed "photographer to the stars" after shooting the likes of US actor Johnny Depp and Princess Caroline of Monaco, Banier became close friends with Bettencourt after meeting her at a dinner party in 1969.
Banier allegedly received gifts worth nearly a billion euros from the heiress, including masterpiece paintings worth €15 million, several cheques and life insurance policies.