The Sick Body Writing: Towards an Affective Genetic Criticism examines the idea that manuscripts can be affected by illness as much as their authors’ bodies are. This article aims to highlight a critical gap in the methodology of literary genetic criticism by introducing a new lens of affective genetic criticism. Genetic criticism looks at the archive of drafts and notes related to a literary work-in-progress. The application of affect theory brings focus to the impacts of the author’s bodily experience during writing while in different states of un/healthiness. The effects of authors’ health on their writing, especially textual non/production and the representations of un/healthiness, can be found in their archive in a variety of forms, whether represented in the narrative or responsible for elements of the narrative’s structure. Using two case studies from different literary canons, James Joyce (modernist) and Aidan Chambers (children’s and Young Adult), the article concludes that this lens can be productively applied to understand better the embodiment of writing processes and adaptations of writing environments as a result of affective needs.