Eusebius traces the Church from Christ’s pre-existent identity as the eternal Word through the apostolic age, persecutions, heresies, martyrdoms, doctrinal disputes, and imperial peace. He presents Old Testament figures and institutions as preparing for Christ, narrates the ministries of the apostles and early bishops, and preserves traditions concerning Abgarus of Edessa, the destruction of Jerusalem, apostolic writings, and the succession of teachers in Rome, Alexandria, Antioch, Jerusalem, and elsewhere. Josephus and numerous ecclesial witnesses support the historical narrative.

Particular attention falls on the witness of Polycarp, Justin, the martyrs of Lyons and Vienne, Origen, Dionysius, and the victims of the Decian, Valerian, and Diocletian persecutions. Eusebius rejects Marcionism, Montanism, Gnosticism, Sabellianism, and other challenges while recording debates over Easter, rebaptism, the millennium, and the Apocalypse. The final books describe Constantine and Licinius’s measures restoring Christian liberty, confiscated property, churches, and public worship, followed by Constantine’s defeat of Licinius and the Church’s renewed peace. A panegyric on the basilica at Tyre presents the restored Church as a spiritual temple founded on Christ, the cornerstone, and inhabited by the Father, Son, and Holy Spirit.