In 1929 he married Alma (Schindler) Mahler, widow of Gustav Mahler, who divorced architect Walter Gropius for him. He was already an established author, but his true claim to international fame came in 1933, when he published The Forty Days of Musa Dagh, a chilling novel which first drew world attention to the Armenian genocide at the hands of the Turks.
An identified Jew, Werfel fled Austria after the Anschluss in 1938 and went to France. With the German invasion and occupation of France during World War II, and the deportation of Jews to the Nazis death camps, Franz Werfel had to flee the country. With the assistance of the American journalist Varian Fry in Marseille, he and his wife escaped the Nazi regime and went to the United States.
While in France, he had made a visit to Lourdes where he found spritual solace. He vowed to write about the experience, and once in America, in 1941 he released The Song of Bernadette. While living in southern California, he wrote his final play, "Jacobowsky and the Colonel" (Jacobowsky und der Oberst).
Franz Werfel died in Los Angeles in 1945 and was interred there in the Rosendale Cemetery. However, his body was later exhumed and returned to Vienna for reburial in the Zentralfriedhof.