In many respects, Sellia had a shared history with Taverna and Catanzaro. The origins of the town are very controversial and scarcely supported by historical evidences. According to official historiographers, Sellia was founded between the 9th and 10th century by a group of refugees from the ancient coastal town of Trischene, who took shelter in mountain areas following the Saracen raids. Trischene had increased the number of its inhabitants because of Greek and Roman settlements in the area, and therefore the town included three settlements. The name, in fact, derives from the Greek Treis Schenè. Saracen invasions depopulated the town and the population scattered and went in search for safer places to live in. The Greek group separated, some of them settled in the middle Simeri Valley and founded an outpost to bar the road to the mountains, others went further into the mountains and founded a stronghold that they called Taverna. The Romans, led by Julo Catimero, settled on Mt Sellion and founded Asilia, present day Sellia, that soon became a defense outpost along the access road to the newly built Taverna. Catanzaro too was founded in the same period.
However, archaeological evidences were found in the surrounding area, suggesting that the town existed much earlier than the arrival of the refugees, that is much earlier than the 9th-10th century. The assumption that Sellia has very ancient origins is also supported by Giovanni Balletta in his book La Calabria nel suo periodo eccelso. The scholar noted that the town of Sellia was present on a map reporting the ancient settlements of Crete island. The number of Sellia inhabitants has greatly decreased so that the mayor of the town decreed that dying was not allowed: the ban was meant to encourage people to take care of their health to control depopulation.