Sustainable entrepreneurship is increasing in importance because it can lead to a socially, economically, and environmentally sustainable society. Firms can solve social and environmental problems and be economically self-sustaining at the same time. Innovation is seen as key to find new solutions for environmental sustainability. Furthermore, scholars see stakeholder engagement as a new solution to create innovations for sustainability and environmental sustainability in particular. Since there have only been few empirical studies in sustainable entrepreneurship and current literature does not sufficiently answer the question how stakeholders are engaged to create innovations for environmental sustainability, we dedicated our study to answer the following research question: How are stakeholders engaged in the creation of an innovative product and/or service for environmental sustainability in sustainable entrepreneurial start-ups from the perspective of the firm? We define sustainable entrepreneurial start-ups as self-sustaining and independent companies that discover, evaluate and exploit opportunities to transition to an environmentally sustainable society. Reviewing the literature on sustainable entrepreneurship, innovation and stakeholder engagement results in a tentative model, which shows the process of stakeholder engagement in sustainable entrepreneurial start-ups. Since the field of study is relatively new, there are some question marks and themes in the model that need to be researched further. We conduct a qualitative exploratory study on German and Swedish start-ups in the fields of renewable energy and energy efficiency with different characteristics to research stakeholder engagement from several perspectives. The data collection technique is semi-structured interviews. We use the abductive approach and the visual mapping strategy in addition to time scales in order to develop understanding of stakeholder engagement. Based on our analysis, we revise the model and show how stakeholders are engaged in sustainable start-ups. Our findings show how different groups of stakeholder such as the team, feedback givers, financial resources givers, technology developers and promoters are engaged to develop the start-ups´ business and innovation throughout the idea- and product development and commercialization. Not only the type of innovation but more aspects such as the relationship to stakeholders and secrecy influence how stakeholders are engaged. Our study has several contributions. For instance, it contributes to stakeholder (engagement) theory and an increased awareness of sustainable entrepreneurial start-ups and their innovative solutions in society. It provides guidelines to start-ups to improve engagement with stakeholders for making their innovations more successful. We recommend further research and give examples of research questions on the topic stakeholder engagement.