In 1928 he moved to Paris and took a post as secretary to the film-maker Jacques Feyder, who then asked him to work on the adaptation of a stage play for his film Les Nouveaux Messieurs.

He went on to write the screenplays for Feyder's most important films of the 1930s: Le Grand Jeu, Pension Mimosas, and La Kermesse héroïque.

Many of these films of the 1930s are marked by a concern for realistic detail with sharply written dialogue, often pessimistic in tone, and several of them provided leading roles which were played by Jean Gabin.

[3] During the German occupation of France, Spaak chose to return to Paris and found work on a number of the wartime productions that were made there, including further films with Duvivier and Grémillon.

)[4] After the war Spaak worked with new directors and in a wider range styles, and he formed a particular association with André Cayatte in a series of films set against a background of the French judicial system: Justice est faite (1950), Nous sommes tous les assassins (1951), Avant le deluge (1953), and Le Dossier noir (1955).