He was prince-bishop of Liège from 1302 until his death in 1312, while serving in the retinue of Henri VII of Luxembourg.
He, however, turned down the position, claiming his background was too humble, and designated Theobald.
Two years later his relative Henri VII of Luxembourg became King of the Romans; Theobald was a close adviser.
When Henry went to Rome in 1312 to be consecrated as Holy Roman Emperor, Theobald accompanied him.
He was a son of Theobald II of Bar, and of Jeanne de Toucy.