Much like traditional sports, esports are susceptible to unsportsmanlike behavior. The first-person shooter (FPS) genre of esports offers proxy views of the world which may promote vicarious gaming with unsportsmanlike conduct impacting spectator experiences. Determining the acceptability of different kinds of player conduct within esports, as well as discerning player actions which violate local norms, may serve to enhance our understanding of sportsmanship in esports. Using a multimethod research design in the context of Counter Strike: Global Offensive (CS:GO) esports, this study aimed to develop a taxonomic classification of (un)sportsmanlike player conduct in the FPS genre, recognizing its various forms. Through analysis of data from structured observations of gameplay, spectator reactions, and semi-structured interviews with players, a generic nodal hierarchical classification with broad application to the FPS genre was refined into a multi-level taxonomy of all forms of sportsmanship in CS:GO. The results highlighted a degree of complexity in the interpretation of sportsmanship in local esport gaming contexts that set it far enough apart from traditional sports to potentially paint a specific picture of ‘esportsmanship.’ The classification is envisaged to enhance our understanding of the sportsmanship in the FPS genre of esports, and guide the thinking of researchers, designers, and testers.