Physiognomy, the art and science of judging a person’s character and potential behaviour by the external appearance of his or her bodily organs on the casus of an analysis of their size, proportion, shape, colour, and texture, and also of the voice, the motion and gestures, has ancient textual roots. The western version of this trans-national practice is founded on ancient Greek texts which were made available to Latin readership in the twelfth and thirteenth centuries through translations of five core texts (some from Greek, other through Arabic or early Latin intermediaries). This newly acquired knowledge flourished in thirteenth-century scholastic culture in the shape of specialised, new compilations, commentaries on core texts (Ps. Aristotelian, or newly assembled manuals), and scholastic questions by natural philosophers and learned physicians. In the West physiognomy was recognised as a science (scientia), which assured its practitioners access to a fuller and more accurate understanding of all aspects of pre-modern psychology (emotional, cognitive, moral and behavioural). This article surveys the pre-1200 physiognomic texts which provided the infrastructure for the evolving scientific discourse of physiognomy in the West. It glances occasionally at Arab physiognomy to draw some broad generalisations about the difference between the two cultures. It then moves to a survey of those medieval thinkers between 1230 and c. 1500 who produced new physiognomic texts, and focuses in the third and main section of the article on an analysis of the key contributions of medieval physiognomic discourse to the longer tradition of physiognomy. Medicinalisation and causal explanation appear to be the main new inputs of the Middle Ages to the long history of physiognomy. It ends with a survey of the uses of physiognomy and its practice between c. 1200 and c. 1500.