His execution, by the Romans in the year 155 AD, was one of the most well-documented martyrdoms in the early church era. The following was based on an eyewitness account of the event:
The [Roman] proconsul was insistent and said: "Take the oath, and I shall release you. Curse Christ."
Polycarp said: "Eighty-six years I have served him, and he never did me any wrong. How can I blaspheme my King who saved me?"...
But the proconsul said: "I have wild beasts. I shall throw you to them, if you do not change your mind."
But he said: "Call them. For repentance from the better to the worse is not permitted us; but it is noble to change from what is evil to what is righteous."
And again [he said] to him, "I shall have you consumed with fire, if you despise the wild beasts, unless you change your mind."
But Polycarp said: "The fire you threaten burns but an hour and is quenched after a little; for you do not know the fire of the coming judgment and everlasting punishment that is laid up for the impious. But why do you delay? Come, do what you will."
And when he had said these things and many more besides he was inspired with courage and joy, and his face was full of grace, so that not only did it not fall with dismay at the things said to him, but on the contrary, the proconsul was astonished, and sent his own herald into the midst of the arena to proclaim three times: "Polycarp has confessed himself to be a Christian."
When this was said by the herald, the entire crowd of heathen and Jews who lived in Smyrna shouted with uncontrollable anger and a great cry: "This one is the teacher of Asia, the father of the Christians, the destroyer of our gods, who teaches many not to sacrifice nor to worship."
Such things they shouted and asked the Asiarch Philip that he let loose a lion on Polycarp. But he said it was not possible for him to do so, since he had brought the wild-beast sports to a close. Then they decided to shout with one accord that he burn Polycarp alive. For it was necessary that the vision which had appeared to him about his pillow should be fulfilled, when he saw it burning while he was praying, and turning around had said prophetically to the faithful who were with him, "I must be burned alive."
Then these things happened with such dispatch, quicker than can be told—the crowds in so great a hurry to gather wood and faggots from the workshops and the baths, the Jews being especially zealous, as usual, to assist with this. When the fire was ready, and he had divested himself of all his clothes and unfastened his belt, he tried to take off his shoes, though he was not heretofore in the habit of doing this because [each of] the faithful always vied with one another as to which of them would be first to touch his body. For he had always been honored, even before his martyrdom, for his holy life. Straightway then, they set about him the material prepared for the pyre. And when they were about to nail him also, he said: "Leave me as I am. For he who grants me to endure the fire will enable me also to remain on the pyre unmoved, without the security you desire from the nails."
So they did not nail him, but tied him. And with his hands put behind him and tied, like a noble ram out of a great flock ready for sacrifice, a burnt offering ready and acceptable to God, he looked up to heaven and said:
"Lord God Almighty, Father of thy beloved and blessed Servant Jesus Christ, through whom we have received full knowledge of thee, 'the God of angels and powers and all creation' and of the whole race of the righteous who live in thy presence: I bless thee, because thou hast deemed me worthy of this day and hour, to take my part in the number of the martyrs, in the cup of thy Christ, for 'resurrection to eternal life of soul and body in the immortality of the Holy Spirit; among whom may I be received in thy presence this day as a rich and acceptable sacrifice, just as thou hast prepared and revealed beforehand and fulfilled, thou that art the true God without any falsehood. For this and for everything I praise thee, I bless thee, I glorify thee, through the eternal and heavenly High Priest, Jesus Christ, thy beloved Servant, through whom be glory to thee with him and Holy Spirit both now and unto the ages to come. Amen."
And when he had concluded the Amen and finished his prayer, the men attending to the fire lighted it. And when the flame flashed forth, we saw a miracle, we to whom it was given to see. And we are preserved in order to relate to the rest what happened. For the fire made the shape of a vaulted chamber, like a ship's sail filled by the wind, and made a wall around the body of the martyr. And he was in the midst, not as burning flesh, but as bread baking or as gold and silver refined in a furnace. And we perceived such a sweet aroma as the breath of incense or some other precious spice.
At length, when the lawless men saw that his body could not be consumed by the fire, they commanded an executioner to go to him and stab him with a dagger. And when he did this [a dove and] a great quantity of blood came forth, so that the fire was quenched and the whole crowd marveled that there should be such a difference between the unbelievers and the elect. And certainly the most admirable Polycarp was one of these [elect], in whose times among us he showed himself an apostolic and prophetic teacher and bishop of the Catholic Church in Smyrna. Indeed, every utterance that came from his mouth was accomplished and will be accomplished....
Such are the things concerning the blessed Polycarp, who, martyred at Smyrna along with twelve others from Philadelphia, is alone remembered so much the more by everyone, that he is even spoken of by the heathen in every place. He was not only a noble teacher, but also a distinguished martyr, whose martyrdom all desire to imitate as one according to the gospel of Christ. By his patient endurance he overcame the wicked magistrate and so received the crown of immortality; and he rejoices with the apostles and all the righteous to glorify God the Father Almighty and to bless our Lord Jesus Christ, the Saviour of our souls and Helmsman of our bodies and Shepherd of the Catholic Church throughout the world.