Praetorian prefect
Under Emperor Valens he was Praetorian prefect of the East (369-377) and consul in 372. During his office as Praetorian prefect he completed the building of the "Cisterna Modestiaca" (a cistern identified with Sarrâdshchane), whose building was begun by the architect Helpidius in 363, while Modestus was "praefectus urbi".