Cooperation and competition have traditionally been considered separate modes of interaction between firms. Recent research, however, observes that firms simultaneously engage in cooperation and competition with each other. Still the interplay of these modes is under-researched and surprisingly little is known about the nature of ‘coopetition’. Ourobjective with this paper is to build new revelatory theory on the various facets of coopetition in vertical IT standardization and discuss their respective implications for environmental sustainability. Werely on an eleven-year study of a standard development effort aimed at greening the Swedish road haulage industry. Framing analysis is appliedto scrutinize relations between cooperative modes and competitive behaviors of participating firms. The findings help explicate how and why stabilized cooperation may render intensified competition thatundermines IT standardization efforts to green an industry. Our theorizing about this paradoxical tension paves the way for future network studies of coopetition dynamics in converging industries.