Purpose-To further extend the understanding of multidimensional engagement of stakeholders embedded in service systems, the purpose of this paper is to explore the antecedents that constitute stakeholder engagement in inter-organizational service ecosystems where stakeholders co-create innovations over time. Design/methodology/approach-An explorative, longitudinal case study design is employed to analyze stakeholders' engagement in co-innovation in an inter-organizational service system in an engineering context. Findings-The study identifies eight antecedents for stakeholder engagement in innovation in the context of a B2B environment. Building on related engagement research, the empirical data show how stakeholder engagement is influenced at both individual and organizational levels by the antecedents friendship, common experiences, self-representation, trust, a common goal, resource dependency, level in the hierarchy, institutional arrangements, and local proximity. Originality/value-The paper extends current understanding of engagement and illuminates stakeholder engagement on a micro level, addressing four key issues for stakeholder engagement in a service ecosystem. How can stakeholder engagement be maintained over time? Does stakeholder engagement at specific hierarchical levels enhance or hinder inter-organizational co-innovation? Is strong engagement necessary for innovation activities? Are the different engagement antecedents linked?