From inventive memes to fan films, contemporary popular culture continues long-standing traditions of adapting existing content to new formats. Despite the centrality of adaptation to popular culture, adaptation studies methods are rarely applied by researchers working in this area. Cosplay, in which enthusiasts dress as characters from popular culture at fan gatherings, is an increasingly visible part of contemporary culture. Through its reliance on a recognized source text, cosplay is a form of vernacular adaptation. By drawing on narrative interviews with cosplayers, this article illustrates how applying key adaptation studies approaches to cosplay can provide a fresh perspective on the fan phenomena. Vernacular adaptation like cosplay is not an esoteric practice. From fan fiction to movie-inspired protest signs, adaptation is a fundamental framework of popular culture. Yet, all too often, the tools and approaches of adaptation studies are ignored by media and cultural studies scholars. Focusing on cosplay as a form of vernacular adaptation, this article will demonstrate that adaptation studies is a valuable, yet overlooked, tool in the study of popular culture.