In 1879 he entered the ministry of foreign affairs as a secretary, and rose gradually through the diplomatic service.

[2] In 1886, he was elected deputy for Aisne, but, defeated in 1889, he returned to his diplomatic career, and on 31 May 1894 accepted the offer of Charles Dupuy to be minister of foreign affairs.

During his ministry he developed the rapprochement of France with Russia—visiting Saint Petersburg with the president, Félix Faure—and sought to delimit the French colonies in Africa through agreements with the British.

This seems to have intensified Hanotaux's distrust of England, which is apparent in his literary works[2] (though most of these were written after he had left the Quai d'Orsay).

His home in Orchaise now serves as a botanical garden, the Parc botanique du Prieuré d'Orchaise.