Since 1803, Clervaux has been the seat of both a deanery (Dekanat) and a parish. Before that, the locality belonged to Munshausen. The first parish church was situated on the present-day market place next to the Grand-rue. From 1910-1912, it was replaced by the current building in the Neo-Romanesque style according to the plans of Johannes Franziskus Klomp, who also designed the Abbey of Saint Maurice. The church is built of local shale stone that harmonises perfectly with the surrounding countryside. The veneration of the martyrs Cosmas and Damian probably reflects the influence of the Diocese of Liège, to which Clervaux belonged before the French Revolution. Around 1700, Count Albert of Lannoy received the relics of these saints from Rome. They are still preserved in the church. The tympanum mosaics above the main portal refer to these patron saints.