The eldest son of the Emperor Carus, he was first appointed Caesar in late 282, then given the title of Augustus in early 283, and made co-emperor of the western part of the Empire by his father.

The elder, Carinus, was left to manage the affairs of the West in his absence, and was later elevated to the rank of Augustus, while the younger, Numerian, accompanied his father to the East.

[5] Carinus acquitted himself well, at least at first, showing some merit in suppressing unrest in Gaul and against the Quadi,[6][7] but the young emperor soon left the defence of the Upper Rhine to his legates and returned to Rome, where the surviving accounts, which demonise him, claim he indulged in all manner of extravagance and excess.

He is said to have persecuted many who he felt had treated him with insufficient respect before his elevation, to have alienated the Senate by his open dislike and contempt, and to have prostituted the imperial dignity with the various low entertainments he introduced at court.

[8] When Carus heard of his son's behaviour in the capital, he declared his intention of removing him from office and replacing him with Constantius Chlorus, who was already known for his ability and virtue.

[9][4][10] At the same time, Numerian was forced to abandon his father's ambitious campaign in the east by the soldiers, who were superstitious about Carus' death, supposedly caused by a bolt of lightning.