His brother Rudolf, Theoderich's uncle, was already elected Archbishop of Trier in 1183, however, he was denied by Pope Lucius III who favoured his rival Folmar of Karden.

Elected archbishop upon the death of his predecessor John I on 15 July 1212,[1] he soon entered into a fierce quarrel with the Rhenish count Henry II of Nassau over the erection of Montabaur Castle on the right bank of the Rhine.

Like his ancestors, he remained a loyal supporter of the Imperial House of Hohenstaufen, backing the young king Frederick II against his Welf rival Otto IV, which earned him the opposition of his counterparts in Cologne and Mainz.

He also ensured the election of Frederick's son Henry (VII) as King of the Romans in 1220 and his coronation by Archbishop Engelbert of Cologne two years later.

He remained a close confidant of the emperor, whom he accompanied to Italy and Sicily, and also of His son Henry (VII) until his rebellion in 1234.