Though often regarded as the first French existentialist, he dissociated himself from figures such as Jean-Paul Sartre, preferring the term philosophy of existence or neo-Socrateanism to define his own thought.

During the First World War he worked as head of the Information Service, organized by the Red Cross to convey news of injured soldiers to their families.

[2] He taught in secondary schools, was a drama critic for various literary journals, and worked as an editor for Plon, the major French Catholic publisher.

In The Existential Background of Human Dignity, Marcel refers to a play he had written in 1913 entitled Le Palais de Sable, in order to provide an example of a person who was unable to treat others as subjects.

[6] For many years, Marcel hosted a weekly philosophy discussion group through which he met and influenced important younger French philosophers like Jean Wahl, Paul Ricœur, Emmanuel Levinas, and Jean-Paul Sartre.

He also influenced phenomenologist and Thomistic philosopher Karol Wojtyla (later Pope John Paul II), who drew on Marcel's distinction between "being" and "having" in his critique of technological change.