Disruptive changes (e.g. new technologies, services, and business models) present a variety of opportunities and risks for companies. They can contribute significantly not only to economic success but also to greater sustainability. Nevertheless, it is not a trivial task for established companies to recognize the potential of disruptive changes and to implement innovations in time. In this context, foresight and openness are proposed as promising approaches. This paper investigates the collaborative open foresight approach for inspiring discontinuous and sustainability-oriented innovations. The results of a longitudinal case study involving two companies show that the participants especially value that collaborative open foresight (1) fosters out-of-the-box thinking (2) supports breaking away from path dependency, and (3) increases the potential of innovations. Most importantly, the joint discussion and analysis of future developments (4) help to generate new insights regarding the opportunities and risks of the disruptive changes identified as well as their potential for discontinuous and sustainability-oriented innovations. It was particularly noteworthy that both companies recognized a significant value-added of collaborative open foresight compared to their previous foresight projects, so far conducted individually, but only one of the two companies could transfer the project's outcome to innovation projects.