The notion that a single firm cannot innovate in isolation serves as starting point for the open innovation paradigm introduced by Chesbrough (2003). In order to improve innovative performance and thereby create value, firms have to engage with other parties to gain access to new ideas or resources (Dahlander and Gann, 2010). The value created and captured by firms opening up their business model should naturally be higher than the sum of the value both parties could have created in isolation, St John and Harrison (1999) describe this phenomenon as ‘synergy’. This master thesis dives into this material in order to derive both theory- and practice-based design principles for the creation of synergy through open business model innovation. These principles are applied in a sustainable business context, to see how two firms collaborating could create sustainable innovations that deliver more value to these firms than the combined effort of their work would have been when working individually. As a result, an open business model template to create four types of synergy has been developed and implemented in a sustainable business context.