Open innovation platforms are a tool to solve sustainability challenges through innovation. These platforms facilitate the collaboration among diverse stakeholders, which is challenging but necessary to solve complex sustainability challenges. However, there is little research on how to design open innovation platforms to support collaboration and feedback from platform members is needed to understand their viewpoints. The study aims to understand the perceived benefits and challenges of participants from sustainability-oriented open innovation platforms. Based on this, the study intends to provide guidance for designing these platforms to increase the benefits for its participants. To understand the different viewpoints better, a qualitative research design in the form of a case study was chosen. Data was collected from interviews with participants from the open innovation platform Climate-KIC and analysed with the help of the Framework method. The results emphasise that open innovation platforms must support their participants throughout the whole open innovation process. Special attention must be paid to the diversity of the participants that require different support from the platform based on their maturity level.