The historian C. W. Previté-Orton states that Tiberius "was really the first of the Greek Emperors, and with him Byzantine becomes the fittest name for the Eastern Empire, which was still Roman in tradition. During his reign, Tiberius II Constantine gave away 7,200 pounds of gold each year for four years.
He was a friend of Justin II, who appointed Tiberius comes of the excubitors. He took control of the empire when Justin II went insane in 574, and to increase his popularity, he immediately began spending money that Justin had reserved in his treasury
Justin II, Tiberius's predecessor, had been made infirm by disease; the faculties of his mind were impaired and he subsequently lost the use of his feet. Confined to his palace, he became a stranger to the complaints of the people and the vices of the government. Conscious of his infirmity, he honorably chose to seek a successor to the Imperial throne. On the advice of his wife Sophia, he handed the diadem to one of his Excubitors, Tiberius. While Justin was still alive, Tiberius' general Maurice fought and defeated the Persians in Armenia. When Tiberius became full emperor upon Justin's death in 578, he extended his military activities into the remnants of the Western Empire, where he made peace with the Visigoths in Spain and defeated the Berbers in North Africa. May have been the Emperor Lucius Tiberius of Arthurian legend, sending envoys to former Roman provinces after a long period without Imperial presence. Meanwhile, the Slavs began to migrate into the Balkans in 579; unfortunately, Tiberius needed the army to defend against Persian invasions, and was unable to stop the Slavic migrations.
In 582, Tiberius fell ill, and Maurice was named his heir. Maurice became emperor when Tiberius died in August - poisoned, it was rumored.