After he was diagnosed with pulmonary tuberculosis in 1919, he rented the castle of Etoy in the Canton of Vaud in Switzerland in 1921 and henceforth would spend several months a year there.
[2] From the 1920s on, Pourtalès published a series of romantic biographies of musicians and also wrote essays, critiques, and journalistic pieces for a variety of French magazines, amongst them the Nouvelle Revue Française.
[2] In 1937, he published La Pêche miraculeuse, the novel for which he is best known today[4] and which won him the Grand Prix du roman de l'Académie française.
[5] Pourtalès's health had been slowly deteriorating, and when World War II broke out, he was severely ill and wouldn't leave Etoy anymore.
The death of his only son and the surrender of France seem to have weakened Guy de Pourtalès,[4][6] who died at Lausanne on 12 June 1941.