His predecessor, Monulphus (Monulf), transferred the seat of the bishopric from Tongeren to Maastricht, which thenceforth was the actual residence of the bishops of Tongeren. However, the official title of the Bishop of Tongeren, episcopus Tungrorum, was retained until the eleventh century, even when the episcopal see had been transferred by Lambert of Maastricht from Maastricht to Liège.
Bishop Gondulphus is a somewhat enigmatic figure indeed, one is inclined to question whether he be not identical with Monulphus. But the two saints must nevertheless be distinguished. Monulphus must have occupied the See of Tongeren until the end of the sixth or the beginning of the seventh century, while a Bishop of Maastricht named Betulphus was present at the Council of Paris in 614. Gondulphus, then, would be inserted between Monulphus and Betulphus, at least if this Betulphus must not be identified with Gondulphus on the grounds that the case is analogous to that of the episcopal list of Mainz, where Bertulfus and Crotoldus must be reckoned identical. Furthermore, the episcopal lists of the eleventh and twelfth centuries, whose value is, however, not very great, ignore the historically attested Betulphus, and make Gondulphus the immediate successor of Monulphus. The biographies of Gondulphus, which are handed down to us from the Middle Ages, are merely an extract from the Vita Servatii of the priest Jocundus. They are quite without value and are full of legends. If they are to be believed, Gondulphus endeavoured to rebuild the town of Tongeren, which had been destroyed by the barbarian invasions. But heaven opposed his scheme, and miraculously manifested its desire to the saint. Furious wolves fell upon the pagan colonists of this region, and devoured them before the eyes of the horrified bishop. Thus has legend quite obscured the authentic history of St. Gondulphus, the fact of his episcopacy at Maastricht being the only one that is authentic. According to local tradition he occupied the episcopal see for seven years and died about 607. This last statement does not tally with his presence at Paris in 614, if he is to be considered identical with the Betulphus who assisted at that council. In any case he was buried in the nave of the church of Saint-Servais at Maastricht, which had been magnificently restored by his predecessor, St. Monulphus.
The bodies of Monulphus and Gondulphus were solemnly exhumed in 1039 by the Bishops Nithard of Liège and Gérard of Cambrai. An epitaph commemorating this event was afterwards misinterpreted, and gave rise to a legend according to which the two saints arose from their tomb in 1039 in order to assist at the dedication of the church of Aachen (Aix-la-Chapelle), and at the conclusion of the ceremony returned to their tomb to resume their eternal sleep.
Together with St. Monulphus, St. Gondulphus is secondary patron of the city and church of Maastricht. His feast is kept on 16 July or 17 June. The commemoration of the exhumation of 1039 is celebrated in August.
St. Gondulphus is known to have been married to Palatina de Troyes, they had a son named Baudgise D'Aquitaine II, who became Duke of Aquitaine, France.