In 1364 he became dean of the Cathedral of Rouen and, his friend Charles becoming King of France on 8 April of that year, Oresme was appointed as Charles' chaplain and councillor.
Sa 1364 siya ay naging dekano ng Katedral ng Rouen, at ang kanyang mga kaibigan Charles pagiging hari ng France sa 8 ng Abril na taon, Oresme ay hinirang bilang Charles' kapelyan at konsehal.