Among the pastoral tasks of the early modern Catholic Church, a fundamental objective was to shape the moral conduct of the faithful in accordance with the Christian ethical system, including matters related to sexual life. The scope of pastoral expectations, however, was adjusted to the environment in which the clergy operated. On the one hand, the promotion of Christian sexual ethics among the peasant or, more broadly, folk strata appears to have been a dominant feature of the moral message conveyed by the Catholic Church in early modern Poland. On the other hand, this effort was often reduced to the most rudimentary principles. Ethnographic sources from the nineteenth century seem to confirm the Church’s considerable success in shaping the sexual ethics of the peasant population in line with its objectives. Yet it must be acknowledged that such portrayals may also reflect the preconceived assumptions of ethnographers of that period. Historical sources from the sixteenth to eighteenth centuries allow us to partially reconstruct the underlying principles of an autonomous peasant sexual ethic—one that the Church actively sought to combat. Its central concern appears to have been the regulation and safeguarding of marriage formation and stability, functions largely overseen by the local community. Building on this framework, the Church attempted to impose its own conceptual system of sin: at times merging it with existing peasant ethics, at other times seeking to correct or transform them. Analysing this process enables us to critically reassess the ethnographic portrayal, which ultimately emerges as a product of these complex interactions.