This article attempts to trace the ways in which Hippocrates’ views on the brain were reconstructed in the Hellenistic and early Roman periods, and how the views attributed to him were increasingly assimilated to Plato’s doctrine on the tripartition of the soul. It points especially to the Hippocratic Letters as a key source for understanding this broader tradition, and argues that Galen’s picture of Hippocratic-Platonic harmony on the soul’s tripartition was directly but tacitly drawing on that tradition.<p></p>