He served under the Eastern Roman Emperor Theodosius I against the usurper Eugenius. Later, when his son Flavius Aetius was born in 396, Gaudentius served as Magister Equitum or Master of Cavalry under the Emperor Honorius. According to The History of the Decline and Fall of the Roman Empire, Gaudentius was still serving the Western Empire in the 420s as Magister militum of the Western Roman Empire. He served under the usurper Ioannes. However, when Ioannes was killed 425, he was forced to serve Galla Placidia and her son Emperor Valentinian III. Gaudentius served as Magister militum from 421 to his death in 432.