A graduate of the École Normale Supérieure in the same class as Roger Vailland, Robert Brasillach, and Maurice Bardèche.
He made a career in journalism and took part in the movement of the Non-conformists of the 1930s, inspired by the personalist generation of young intellectuals who shared some of the ideals of the Action Française, holding right-wing beliefs as an answer to a "crisis of civilization" and materialism.
At the same time, he joined Jean de Fabrègues in the creation of a more analytical paper, Combat, one which would be published until France's defeat in World War II.
A regular contributor to L'Action française since 1938, Maulnier continued to publish after Nazi Germany's occupation of France (from 1940); he also started writing for Le Figaro.
He ceased writing for the paper after the start of Operation Torch in 1942, and remained a journalist for Le Figaro from 1945 until his death.