He was born in Italica, Hispania Baetica, which was also the birthplace of Publius Aelius Hadrianus Afer, the emperor Hadrian's father.
When Afer died about 86, Attianus and the future Emperor Trajan (another native of Italica) became the ten-year-old Hadrian's guardians.
[1] Otherwise nothing is known of Attianus's early career, but towards the end of Trajan's reign he was joint Praetorian Prefect with Servius Sulpicius Similis.
Shortly before his death, Trajan was said to have composed a letter naming Hadrian as his adopted son and successor.
However, the new emperor resented Attianus's power, and, in 119, induced him to request to be relieved of the post of Praetorian Prefect.