In 1633 the authorities of the city of Rouen in France arrested some of the most prominent members of the Rouennais Portuguese merchant community, whom they accused of the crime of "judaizing." This article examines that incident, and its ramifications for the Portuguese in Rouen. Most of the Portuguese merchants and their families who settled in Rouen in the sixteenth and seventeenth centuries were conversos or converted Jews, and many still secretly practiced Judaism. The arrests exposed and exacerbated a division within the Portuguese community over strategies of coexistence within Rouennais society, between those who wished to maintain their Jewish religion and those who considered themselves Christian and sought to assimilate into French society. Although royal intervention led to the release of the arrested Portuguese, the incident contributed to the dispersion of the Portuguese community in Rouen.