He followed a military career: between 441 and 443 he is attested as dux or magister utriusque militiae. In 441 he was in Tarraconensis (Spain), where he defeated the Bagaudae. In 443 he was succeeded by his son-in-law Merobaudes.
He was appointed consul for the year 449. At the beginning of his office he was in Gaul (probably in the capital city of the praetorian prefecture, Arelate), and Nicetius delivered a panegyric in his honour.
A consular diptych produced by Astyrius in 449 is preserved at Liège. The diptych shows Astyrius seated on a curule chair wearing complete consular regalia and the inscription Flavius Astyrius vir clarissimus et inlustris comes ex magistro utriusque militiae consul ordinarius.
Fl. Rufius Praetextatus Postumianus,
| Consul of the Roman Empire
with Fl. Florentius Romanus Protogenes
Imp. Caes. Fl. Placidus Valentinianus Augustus VII,