He was born in 1925, and served in the French Army, specifically in the 2nd Hussard Regiment in the Second World War (Until 1945).He began to write quite early in his life. His first novel, Les Épées (The Swords) was published in 1948, when he was only 23.

He was the leader of the Hussards, a literary group which included notably Antoine Blondin, Michel Déon and Jacques Laurent, opposed to existentialism. He was opposed to the figure of the "engaged writer" symbolized by Jean-Paul Sartre.His most famous work is considered to be Le Hussard bleu published in 1950. Nimier also wrote in monarchist review La Nation française.

He also worked with director Louis Malle on the screenplay for Malle's 1958 film Ascenseur pour l'échafaud.