This chapter offers a comparative analysis of the territories along the southern Baltic littoral, namely Poland, Pomerania and Mecklenburg, with a primary focus on identifying the overarching patterns in the development of the Reformation in the region. The emergence and dissemination of the Reformation in the Baltic region can be traced back to Martin Luther’s prominent public appearance in Worms in 1521. Subsequently, the reform movement rapidly transcended the political and ecclesiastical boundaries in this area. Drawing upon pre-existing institutional frameworks, this article delves into the mechanisms behind the propagation of the new religious message, the establishment of reform networks and the responses of secular authorities. By shedding light on the content of Evangelical preaching and the phenomenon of Baltic iconoclasm, this study aims to discern the identity of the earliest proponents of the burgeoning reform movement. The chapter argues, however, that the subsequent monolithic Lutheran character of the region was a result of the collective decision of princes and secular authorities to adopt the Reformation according to the Wittenberg model.