© francesco quatrini, 2021This essay focuses on the presence of Polish Brethren (usually known as Socinians) exiles in Amsterdam in the mid-seventeenth century, examining the social and intellectual interrelations between them and other Dutch religious minorities. It describes the phenomenon of the Brethren's emigration to the United Provinces, roughly between 1638 (when the Socinians were banished from Raków) and the late 1660s, relying on both published and manuscript sources. It particularly emphasizes the social relations that the Brethren established with the Remonstrants, the Mennonites, and the Collegiants. It then focuses on the last group and argues that shared views on religious tolerance were the common intellectual ground that likely contributed to the friendly relationships between the Brethren and the Collegiants. It also argues that these relationships fostered further intellectual crossovers between the two groups, as the Brethren in Amsterdam were influenced by the Collegiants' emphasis on freedom of prophesying, egalitarianism, and anti-confessionalism.