The interpreter took his case to French court after his visa application was rejected in 2015.
French authorities have been given a week to ensure the safety of the interpreter and his family by relocating them to a secure part of the Afghan capital, Kabul, while his request is reconsidered over the next two months.
Caroline Decroix, vice-president of a group of former Afghan interpreters, said the decision could provide a lifeline for other former aides to the French army who face threats at home because they are considered traitors.
"The ruling by the Conseil d'Etat gives the right of protection to aides and assistants. That means all those whose requests have been refused will have the right to appeal."
More than 800 Afghans were employed by the French army up until its withdrawal in 2012.
Only 173 Afghan temporary recruits have obtained visas to come to France.