The Historia Augusta claims that he was the foremost of Valerian's military commanders, but that is most likely a gross exaggeration, if not entirely fictitious.

With the support of Balista, one of Valerian's military commanders, and with the influence that possession of the treasury of Valerian brought, Macrianus managed to have his two sons Macrianus Minor and Quietus elevated to the throne.

Macrianus Major and Minor marched the eastern army from Asia to Europe, but were defeated in Thrace in 261 by Aureolus.

According to Joannes Zonaras, their army was encircled by Aureolus and surrendered, except for the Pannonian legions.

[6] Macrianus asked to be killed with his son to avoid delivery to Aureolus.