After serving as minister for Justice and Religion, D\'Anethan was named the 12th Prime Minister of Belgium and Minister of Foreign Affairs by King Leopold II on 2 July 1870. During his term in office, d\'Anethan was responable for directing the Belgian reaction to the Franco-Prussian War.
D\'Anethan and the king agreed a programme whereby the King\'s favoured military reforms—in particular the abolition of Remplacement conscription—would be implemented, along with an agreement not to institute electoral reforms. He served as Foreign and War minister in his own government.
D\'Anethan was obliged to include in his cabinet ministers who were opposed to the abolition of Remplacement which led to conflicts with the King. A political crisis following his nomination of Pierre de Decker as governor of Limburg led to the resignation of d\'Anethan\'s government.
He later served, from 1884 to 1885, as president of the Belgian Senate.