Coopetition entails tensions inherent to collaboration with competitors. This paper focuses on the coopetition formation stage and its effects on the development of tensions. We performed interviews with executives of coopeting firms, create case studies of organizations that initiate and execute coopetition agreements for other firms, and then study firms engaged in mutual coopetition. While this study confirms previous findings that coopetition formation can be deliberate or emergent, it also reveals that the two approaches differ in strategy development patterns, which influence the type and intensity of tensions, as well as the scope and sustainability of the coopetition. The deliberate approach mainly includes tensions due to lack of trust, knowledge exposure and cultural gaps, and the scope and timeframe of the coopetition are clearly delimited. Previous acquaintance and existing trust correspond to a lower intensity of tensions for the emergent approach, and the scope and timeframe are open for extension.