His father, Josep Oriol Mestres [ca], was an architect who participated in numerous major project, including the demolition of the city walls.
He attended a French secondary school, and studied at the Escola de la Llotja, where he showed a talent for caricatures.
He made several extended visits to Switzerland with his friend, the journalist and playwright, Pompeu Gener [ca], where he was influenced by Swiss federalism, the poetry of Heinrich Heine, and the comic drawings of Rodolphe Töpffer.
Their home, a narrow apartment in the old part of town, with a garden of hydrangeas on the roof, became a meeting place for the creative community of Barcelona.
In 1915, he wrote a book of poems about World War I, Flors de Sang (Flowers of Blood), which gained him several awards, including a Cross of the Legion of Honor, from the French government.