While rethinking their business model (BM), incumbents increasingly rely on alliance partners to provide additional resources. The resulting business model innovation alliance (BMIA) focusses on the joint commercialisation of the alliance results via a shared BM. Our findings from an in-depth case study show differences between BMIAs and more common types of alliances, such as development alliances, regarding three dimensions: dynamic, relational and architectural. On this basis, we developed an integrative framework, by combining our results, with Amit and Zott’s BM design framework that enables firms to open up their BM in order to exploit the full potential of BMIAs for BMI. In addition, we contribute to extant literature on BMI by introducing BMIAs as a means to BMI in established firms. Furthermore, we close the gap between open innovation and BMI literature by illustrating how to open up the BM in order to tackle the challenges arising from BMIAs.