The relevance of alliances has increased significantly over the last few decades. While traditionally the relationships among competitors were seen as based on competition, recently a new approach, called co-opetition, sees the same relationships based on the cooperation among companies. Specifically, co-opetition is a concept that combines competition and cooperation, meaning that two or more competitors cooperate in order to create a bigger business pie, by simultaneously competing for bigger pieces. This paper analyzes a successful case of co-opetition in the context of Italian space and defense industries. The analysis is proposed in the form of a case study-based research, which was carried out through a questionnaire survey and some field interviews with managers of a consortium and an engineering company belonging to the consortium investigated, specialized in the design and implementation of complex applications. By presenting a successful case study, this paper aims to highlight the benefits of the co-opetition model undertaken by the company, thus providing useful guidelines for co-opetition in similar context.