The shipping industry faces huge challenges with regard to improving its environmental performance. The current regulatory approach has not been successful. Public and private actors increasingly rely on partnerships. The literature on partnerships for sustainability has contributed to a better conceptualisation of the subject. However, less is known about the processes and the outcomes of the partnerships as well as interactions between partnerships. This paper aims to improve the understanding of how partnerships contribute to developing cleaner technologies in the Danish shipping industry. Two partnerships have been analysed: Partnership for Cleaner Shipping and the Green Ship of the Future. Participation, scope and division of roles among partners have influenced both partnerships. Furthermore, both partnerships have developed organisational forms that 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.