During the eighteenth century, orders of nursing sisters took on an expanded role in the rural areas of Brittany. This article explores the impact of religious change on the medical activities of these women. While limits were placed on the medical practice of unlicensed individuals, areas of new opportunity for nuns as charitable practitioners were created by devout nobles throughout the eighteenth century. These nuns provided comprehensive care for the sick poor on their patrons’ estates, acting not only as nurses, but also in lieu of physicians, surgeons, and apothecaries. This article argues that the medical knowledge and expertise of these sisters from the nursing orders were highly valued by the elites of early modern Brittany.