This article considers the effects of the First World War on gender relations as they are perceived and represented in Colette's 1926 novel La Fin de Chéri. It discusses two interconnected aspects of the novel's evocation of the upper echelons of post-war French society. First, it focuses on the ways in which the novel intersects with the 1920s debate on gender identity, which conflates with a more generalized sense of cultural despair that was discernible after 1918 in diverse political, social and literary discourses. Whereas some commentators have argued that the novel reproduces reactionary and anti-feminist post-war stereotypes, this article suggests that the ambiguities evident in the figures of Edmée and Chéri work to reveal the inconsistencies and limitations of the ideals of femininity and masculinity that were widely promoted during this period. Second, the article examines in more detail the depiction of a returning soldier suffering from war-induced neurasthenia. I argue that the eponymous hero's psychological trauma is contrasted with Léa's more positive adaptation to a post-war world. I conclude, however, that Colette's novel equally flags up the difficulties inherent for both characters as they attempt to negotiate a space for their identity within the competing gender discourses of 1920s France.