Identity construction as a form of institutional work has mainly been studied from discursive perspectives. We examine how the identity of start-up entrepreneurs is constructed within the sociomaterial setting of a major start-up and technology conference, to enhance institutionalization of start-up entrepreneurship. We draw from the theories of performative identity construction, sociomateriality, and affect. Our study contributes to research on institutional work by highlighting the sociomaterial and affective nature of identity construction as a form of institutional work. We demonstrate how the identity of a start-up entrepreneurs is constructed as rock star, vital entrepreneur, and buddy in a start-up ecosystem. Further, we present characteristics of sociomaterial agency that strengthen identification with the institution of start-up entrepreneurship: multisensority, temporal multidimensionality, and the dynamics of equality and exceptionality building. Our study also critically demonstrates how constructed identities tend to reinforce the link between entrepreneurship and masculinity.