The French government confirmed their release and said they were all in good health.
A total of seven hostages including four other French nationals were seized in September in the west African country's uranium-mining town of Arlit and later taken into Mali.
Since then the group was scattered and moved outside the country.
One of the freed hostages, Frenchwoman Francoise Larribe, was suffering from cancer and was undergoing chemotherapy treatment shortly before she was abducted.
The group's abduction was claimed by Al-Qaeda in the Islamic Maghreb (Aqim), whose leader warned France to pull its troops out of Afghanistan if it wanted to see the safe return of the French hostages.
The north African branch of Al-Qaeda operates in a vast desert area across Algeria, Mauritania, Mali and Niger, where it carries out attacks, trafficking and kidnapping of Westerners.
In January Aqim kidnapped two 25-year-old Frenchmen from a restaurant in Niamey, but the victims were killed in Mali after a failed attempt by French special forces to rescue them.