In this work, the printed Greek confession books are subjected to extensive analysis for the very first time. These books, which appeared at the beginning of the 17th century in the orthodox East, enjoyed unprecedented popularity in their time. This work focuses on analyzing the origins of these confession books and their sources, within the context of church policy. Through new findings, which radically revise the knowledge accrued through previous research, it makes an essential contribution to research on the history of Orthodoxy under Ottoman rule.