Lassana Bathily, who has lived in France since 2006, had applied in July last year for French nationality, said Interior Minister Bernard Cazeneuve in a statement on Thursday, praising his "bravery”.
24-year-old Bathily, who is Muslim, was an employee at the supermarket and was working when the assailant Amedy Coulibaly stormed in. Bathily quickly took everyone downstairs to the cold store.
He told everyone to remain quiet, fearing the attacker might come after them, he explained to BFMTV afterwards.
He then unplugged the freezer, turned off the light inside and kept a lookout.
After some time a colleague came down and said Coulibaly had figured out more people were hiding downstairs and was demanding that they come up.
If not, he threatened to come down and shoot everyone.
That's when Bathily said he decided to escape using the delivery lift to the emergency exit.
Once outside, police initially thought he was an assailant and he was hand-cuffed for an hour and a half.
Once it was understood that he was not involved in the attack, the police were glad of his help and information he could give them.
His mother joined the family of slain police officer Ahmed Merabet in an appeal against Islamophobia and anti-Semitism in the aftermath of last week’s attacks.