Upon the death of his father in 1816, he became the 8th Duke of Rohan, and Count of Porhoët in 1816, and inherited the family seat, the Château de Josselin, which had been damaged during the Revolution.

[4] After the death of his wife, he devoted himself to the church, entering the Saint-Sulpice Seminary in Paris, from 1819 until 1822.

When he entered religious orders, his younger brother, Fernand, took the title, Prince of Léon.

He was ordained on 1 June 1822, and preached at La Roche-Guyon before becoming Vicar General of Paris.

The fall of the Bourbon monarchy after the July Revolution of 1830 forced him to flee to Belgium and then Switzerland.