The two marines, stationed at a French naval base in the southern city of Toulon, were arrested on Monday by the DCRI, France’s central intelligence directorate, army secret service, and the anti-terrorist division of France’s judicial police.
The men are accused stealing military-owned bullet-proof jackets and heavy-duty helmets.
They were arrested in connection with a probe into a terror cell implicated in an anti-Semitic bomb attack near Paris last September, it was revealed on Thursday.
A brother of one of the suspects is believed to be an Islamist extremist fighting with anti-Assad rebels in Syria.
According to sources cited by French radio Europe 1, investigators probing the terror cell had been keeping the jihadist militant under surveillance in Syria.
Upon learning that his brother was serving in the French military in Toulon, intelligence agents then placed the 23-year-old marine under watch over the last few months.
In the course of that surveillance, he was found to have purchased the stolen equipment from another marine.
Both men were arrested on Monday. The marine accused of purchasing the material has been kept in custody until Thursday.
The 23-year-old was due to leave the French military in July and begin a career in private security, Europe 1 reported.
The ongoing investigation centres around whether the stolen bullet-proof vest and helmets were intended to be used in a new job in private security, or for terrorist activity.
The September grenade attack on a kosher supermarket in Sarcelles sparked a major anti-terrorist investigation which led to the discovery of bomb-making equipment and the arrest of 12 suspected members of a jihadist cell near Paris in October.
The suspected leader of those detained, 33-year-old Jeremie Louis-Sidney, was shot dead in October last year after he opened fire on officers seeking to arrest him in a dawn raid at his home in the eastern city of Strasbourg.
A list of Jewish organisations in the Paris area was found at one of the addresses where the bomb-making components were discovered.
The Sarcelles grenade attack was one of the most high profile incidents of anti-Semitism, which soared by 82 percent in 2012 according to a worrying report.
Last year also saw the murder of four Jewish people in Toulouse, including three children by self proclaimed Al-Qaeda inspired gunman Mohamed Merah.