A video posted to the website YouTube shows the seven hostages kidnapped by al-Qaida-linked militants in Niger.
The video was posted to YouTube and some jihadist websites on Thursday.
It shows a series of still photos, accompanied by an audio recording in which several people are questioned in French about their nationality, families, and the conditions of their abductions.
The speakers all name Al-Qaida in the Islamic Maghreb as their abductors and say they are still being held by the Islamist militant group.
The French foreign ministry said the photos are authentic, and called them "an encouraging sign" in that they show the hostages to be alive.
Gunmen kidnapped five French nationals and two Africans on September 16 in the town of Arlit in northern Niger. Officials have said they believe the hostages are now in neighboring Mali.
In the images, the seven people are sitting in a row on sandy ground. A row of armed men wearing turbans stands behind them. Two armed men also sit on the ground, and a number of sport utility vehicles can be seen behind the group.
One face has been blurred in the images. That may be the sole woman captured.
Al-Qaida in the Islamic Maghreb has claimed responsibility for the kidnapping. France's defense minister says French officials have been waiting for the kidnappers to make their demands.
France has sent a military intelligence unit to the region, but has said it wants to open communication with the militants in hopes of freeing the hostages.
The captives include two employees of the French nuclear energy firm Areva and five with a subsidiary of the French construction company Vinci.
Al-Qaida in the Islamic Maghreb has carried out previous kidnappings in the region, including that of a 78-year-old Frenchman who was abducted in Niger in April and later killed.