He was suffect consul in the year 146, following the death of Sextus Erucius Clarus in March, serving until the end of June; his colleague was Gnaeus Claudius Severus Arabianus.
Mireille Corbier interprets the combination of this position and a lack of service as a military tribune as making him "predestined for an administrative career".
[3] His next posting was as quaestor to the proconsular governor of Africa, and upon completion of this traditional Republican magistracy Modestinus was enrolled in the Senate.
[6] While being prefect of this treasury in most cases led immediately to the consulate, Modestinus was instead governor of the public province of Achaea for the term 144/145.
These included membership in the collegium of the fetiales, in the sodales Augustales, and in the Quindecimviri sacris faciundis, the Roman priesthood entrusted with the care of the Sibylline oracles.