An Egyptian officer in the Roman navy, Isidore confessed himself as a Christian to the commander of the fleet while they were on the Aegean island of Chios.

Because he was unwilling to repent and worship the gods of the state, he was tormented and beheaded, and his body cast into a cistern.

[2] According to tradition, his friends Ammonius and Myrope, both destined to martyrdom, would have retrieved the body and interred it properly.

St Isidore's veneration spread in all the Mediterranean sea and he became a sailors’ protector.

In 1125, his remains were brought from Chios to the Venetian Basilica of St. Mark, which contains a small chapel containing the sarchophogus.