This study aims to reveal the determinants of the emergence of coopetition strategy in R&D programs. This qualitative research is based on an exploratory case study: the cluster Celtic-Plus, dedicated to wireless telecommunications within the Eureka program. Our results show that several factors are necessary for coopetitive projects to emerge: a favorable context for collaboration, research-oriented objectives, consistency with the strategy of member firms, and a portfolio of R&D projects represented in several European, national, and regional R&D programs. This research shows how the degree of maturity of technology shapes a firm’s choice of coopetition strategy. Competitors work together to render technology maturer but without arriving at the development of final products and services stage. This strategy creates a time-lag between the cooperative and the competitive behaviors of the coopetition strategy. The study concludes with guidance for firms choosing a coopetition strategy.