This paper considers the artist Arnold Houbraken (1660-1719) as an unconventional Christian and sheds new light on his representation of artists from religious minority groups in his Great Theatre of Netherlandish Painters and Painteresses (1718-1721). By exploring Houbraken's years within the Flemish Mennonite milieu in Dordrecht (1660-ca. 1685) and investigating his representation of religious difference in his biographies within The Great Theatre, this study extends scholarship on Houbraken beyond the current focus on his later years as a writer in Amsterdam, and it offers findings on the experience and reception history of nonconformists and religious minority group members, like the spiritualist David Joris and the Mennonite martyr Jan Woutersz van Cuyck (among others), within the Dutch art world. The paper also addresses the historiographical disconnect between literature in the disciplines of art history, intellectual history, and history of religion that persisted until very recently regarding Houbraken's status as a heterodox Enlightenment thinker.