Recent literature on open innovation (OI) highlights the need for studies regarding the factors that influence firms to switch from a closed to an OI strategy. At the same time, stakeholder literature points out the scarcity of knowledge regarding antecedent factors fostering collaboration with the firm's stakeholders and their engagement for higher value creation. To fill these gaps, we propose an analytical framework for implementing a strategic OI process through the development of stakeholder engagement. Our framework comprises 17 factors grouped in five levers: knowledge, collaboration, organizational, strategic, and financial. We empirically applied this framework to two industrial SMEs. A qualitative study was conducted based on semi-structured interviews with internal and external stakeholders of both firms. The results show that one company successfully implemented the OI process, while the other struggled to evolve from a traditionally closed innovation model to a more open model. Analyzing the results, we identified several aspects that could explain this difference. These aspects concern the OI activities performed by both firms, the combination of the five levers into a coherent OI approach, stakeholder engagement, and the characteristics of the CEOs. The current study contributes insights for theory and practice, especially as it proposes an original framework for developing a strategic OI process that integrates a stakeholder approach.