The article takes stock of the historiographical debate on religious coexistence in the Early Modern period, and on the presence of foreign Protestants in the Italian peninsula in the early seventeenth century. In particular, it shows how the Thirty Years’ War was a significant turning point, both if we look at the Inquisitorial attitudes towards heterodox foreigners, and to the Protestant propaganda initiatives in Italy. The article demonstrates that there were numerous strategies for religious coexistence between Catholics and Protestants, and how only few of the latter were involved in proselytizing. In the mid-seventeenth century, the circulation of reformed texts in Italy would finally end up corroborating the individual libertine dissent, rather than building a confessional Protestant presence in Italy.