Galen (129–ca. 216) left a significant number of writings, over 100 treatises in a modern edition, which represent some 12 percent of ancient Greek literature. Although Galenism dominated the tradition of Western medicine, knowledge of his writings was relatively limited during the Middle Ages. The substantial body of these writings was made available in Europe thanks to the Aldine Greek edition (Venice, 1525), followed by a flood of Latin translations. In my paper, I will examine the impact of some key texts of Galen at the threshold of early modern science and philosophy. To this end I will focus on the particular use of Galen’s writings and teachings by Jean Fernel (1497–1558) of Paris, one of the most influential physicians of the Renaissance, and other physician-philosophers who were his contemporaries and followers in the late sixteenth and early seventeenth centuries.