Christine de Pizan has attracted recent scholarship as both Europe’s first ‘proto-feminist’ and as a prolific medieval writer. Fashion plays a prominent role in both the text and imagery of her manuscripts, yet this aspect of her oeuvre has not received in-depth scrutiny. What Christine has to say about fashion is informative of fashion’s practical and symbolic functions in medieval society. A study of dress in her works also enriches our understanding of Christine’s viewpoints. Fashion is represented in two mediums in Christine’s manuscripts: through written text and visual manuscript illuminations. By analysing Christine’s advice and attitudes regarding female dress in her conduct manual, The Treasure of the City of Ladies (Trésor), the first chapter will reveal how clothing was a genuine social concern with significant social, moral and economic connotations for women. Fashion functioned as social regulation, yet could provide medieval women with the means to express themselves and control how they were perceived. The second chapter will draw on the concepts of the first chapter to analyse how Christine utilises fashion’s social, moral and economic connotations to build her authority as an author. Her attitudes towards the conventions and proprieties of fashion in the Trésor inform the meaning of these images and how she wished to be perceived. Fashion is a potent source of information about Christine and medieval culture in her opus. This analysis proves the worth of studying fashion as an historical source. This study of Christine’s oeuvre illustrates how fashion ‘speaks’ and analysing it can enrich our understanding of the past. Just as fashion is not merely decorative in Christine’s oeuvre, fashion history is not a frivolous field. In this dissertation, fashion history is shown to be a legitimate mode of enquiry that has value across a range of historical disciplines.