Georges, the eldest, would head the operations of the studios, while Fernand would concentrate on the artistic side and business development.

In 1923, Mourlot won a contract to produce an original lithographic poster to promote an exhibition of French Modern Art in Copenhagen, Denmark.

A few years later, through the friendship he had developed with the writer Georges Duhamel, himself a former veteran of World War I, Fernand Mourlot met the painter Maurice de Vlaminck.

1930 marked the start of another important and long lasting cooperation: the one between Mourlot and the director of the French National Museums.

That year, two more historically important posters for Pierre Bonnard and Henri Matisse would be created for the exhibition of the Art Independent at the Petit Palais.

Fernand Mourlot spent most of his time with the fictitious administration of other printing studios (Imprimerie Union), owned by Jewish friends and colleagues, thus avoiding the forced transfer of their assets to the state, and to the production of forged identification papers.

The first was a collaboration with the gallery owner Louis Carré that would bring works with Georges Rouault and Raoul Dufy; the other was an introduction by the writer Jean Paulhan, to the artist Jean Dubuffet and the first book publishing ventures by Fernand Mourlot in 1944, with the creation of "Les Murs", poems by Guillevic and "Matiere et Memoire" with a text by Francis Ponge.

In October 1945, encouraged by Henri Matisse and Georges Braque, Pablo Picasso meets with Fernand Mourlot.