In 533, Sardinia returns to the rule of the Eastern Roman Empire (in this period sometimes referred to as the Byzantine Empire) when the Vandals are defeated by the armies of Justinian I under the General Belisarius in the Battle of Tricamarum, in their African kingdom; Belisarius sends his general Cyrillus to Sardinia to retake the island.

Sardinia remains in Byzantine hands for the next three hundred yearsaside from a short period in which it is invaded by the Ostrogoths in 551.The dates and circumstances of the end of Byzantine rule in Sardinia are not known.

Direct central control is maintained at least through c. 650, after which local legates are empowered in the face of the rebellion of Gregory the Patrician, Exarch of Africa and the first invasion of the Umayyads in North Africa.

The loss of imperial control in Africa leads to escalating Moorish and Berber raids on the island, the first of which is documented in 705, forcing increased military self-reliance in the province.

Communication with the central government becomes daunting if not impossible during and after the Muslim conquest of Sicily between 827 and 902.

A letter by Pope Nicholas I as early as 864 mentions the "Sardinian judges", without reference to the empire.