The teaching of Christ and of the Antichrist have a central place in Flacius’s theological thinking about the church. In his struggle for the truth of the Gospel and the Word of God, Flacius points to the Antichrist and his teaching, which is opposed to the pure Word of God. In this article we will first define terms and provide an overview of biblical teaching about the Antichrist. After that we will outline the theological thoughts about the Antichrist in the time of the Reformation. Flacius’s theological thoughts about the Antichrist, as well as Christ’s versus Antichrist’s teachings, are taken from his works, A Brief Overview of the Faith of Jesus Christ and of the Antichrist (Breves Svmmae Religionis Iesu Christi, & Antichristi, per Matth. Flacium Illyricum), A Paper Against Papal Primacy (Scriptum contra primatum papae, ante annos 100. compositum. Item, Matthiae Flacij Illyrici de eadem materia), and The Catalog of the Witnesses of Truth (Catalogus testium veritatis), as well as from gaining insight into his other works. In his deliberations, Flacius joins the majority of the 16th century Reformers, as well as the numerous gospel preachers in previous centuries, emphasizing that the Word of God is the only and supreme authority in the church. With a strong emphasis on the authority of the Bible, Flacius attempts to challenge the pope’s authority and primacy, thus strengthening the Protestant churches, which were founded during the Reformation, and to weaken the Roman Catholic Church, led by the pope. By comparing the papacy with the Antichrist, Flacius calls the hesitant to turn to God, accept the teachings of the Bible, reject all human teachings and traditions, separate themselves from the Catholic Church, and join the Evangelical Church, whose teaching relies solely on the Word of God.