The shipping industry is confronted with stricter environmental regulations and societal pressure concerning its environmental performance. However, a command and control approach has not succeeded in facilitating the development of cleaner industries. With this goal, key public and private actors increasingly rely on partnerships and in Europe several partnerships have been created for the development of environmental technologies in the shipping industry. While the literature on partnerships with a focus on sustainability has contributed to a better conceptualization of the subject, a gap exists on the interactions of: firstly, institutions and actors in partnerships; and secondly, two or more initially independent partnerships. This paper aims to improve the understanding of how partnerships contribute to developing cleaner technologies in the Danish shipping industry by shedding light on the processes and the outcomes of two separated partnerships (Partnership for Cleaner Shipping and Green Ship of the Future) and the interactions of the two partnerships. In terms of processes, the partnerships are influenced by the participation, scope and division of roles among partners. In relation to outcomes, the first salient issue is that both partnerships have developed organizational forms which proved to overcome the tensions in traditional partnerships, between open and information-based networking on the one side and closed and development-oriented collaboration on the other side.