Euphemia's name and year of death are recorded in the 5th century Martyrologium Hieronymianum, the earliest extant list of Christian martyrs.

[1] Egeria, who made a pilgrimage to the Holy Land about 381-384 and wrote an account of her travels, relates being shown the site of Euphemia's martyrdom in Chalcedon.

According to tradition, she was the daughter of a senator named Philophronos and his wife Theodosia in Chalcedon, located across the Bosporus from the city of Byzantium (modern-day Istanbul).

According to the Synaxarion of Constantinople, a collection of hagiographies, both parties wrote a confession of their faith and placed them on the breast of Saint Euphemia within her tomb.

[1] When the persecution of Diocletian ended, the Christians laid Saint Euphemia's reputed relics in a golden sarcophagus, placed within a church that was dedicated to her.

There, during the persecutions of the Iconoclasts, her reliquary was said to have been thrown into the sea, from which it was recovered by the ship-owning brothers Sergios and Sergonos, who belonged to the Orthodox party, and who gave it over to the local bishop who hid them in a secret crypt.

[5] The primary feast day of Saint Euphemia, celebrated by both Eastern and Western Christians is September 16 in commemoration of her martyrdom.