Their release coincided with talks in Chad between Mr Sakozy and President Idriss Deby.
Ten other Europeans, French and Spanish citizens, are still being held over an alleged attempt to take 103 children out of the country.
Mr Sarkozy said he hoped those still in custody will be treated fairly.
He also stressed the affair would not affect relations between France and Chad or derail plans to deploy a European force to protect refugees in Chad and in the neighbouring Central African Republic.
The foreigners were jailed along with four Chadians after the French charity Zoe's Ark was stopped from flying 103 children from eastern Chad to France where they were to be placed in the care of host families.
The group claim they were orphans from the war in Sudan's Darfur region, across the border from Chad.
But the Chadian government has dismissed the claim, and aid agencies say most of the children have families and actually come from Chad.
The six remaining French nationals face charges of attempted kidnapping, while three other Spanish flight crew members are accused of complicity. If convicted, they could be sentenced to up to 20 years of forced labour.
