The aim of this article is to research into the relationship between fiction and aesthetics in the novel La vida breve (1950) by Juan Carlos Onetti. The methodology is constructed with the help of two fundamental studies which focus on literary fiction, Teorías de la ficción literaria (1997) by Antonio Garrido Domínguez and Poética de la ficción (1993) by José María Pozuelo Yvancos. Theories on fiction have traditionally been developed in the fields of philosophy, linguistics and literature. Upon reviewing previous studies on this topic it becomes clear that, even though there exist some analyses, fiction is not their centre of attention (it is not the main topic). Finally, in the development of the research, it is shown in what sense La vida breve is a metafictional novel, and how Onetti falls within a tradition of writers such as Cervantes, Borges and Cortázar, among others. © 2021 Liverpool University Press. All rights reserved.