The early stages of World War I, with Romania maintaining neutrality, saw Rosetti campaigning for the Central Powers. He advised against any alliance with the Russian Empire, being fearful of Pan-Slavism and supportive of the Romanian claims in Bessarabia. He was disappointed when the country sided with Russia, and remained behind in Bucharest when it was occupied by the Central Powers; with Carp and other Conservatives, he organized a collaborationist bureaucracy, and served in it as Ephor of the Civilian Hospitals. Such choices contrasted those of his son, who became a war hero. Reunited with him in postwar Greater Romania, Rosetti still pursued his literary career, receiving accolades for his final works as a memoirist and raconteur. One of his "Moldavian tales" was adapted for the screen by his son-in-law, Victor Beldiman.