With ubiquity of the Internet and social platforms, open innovation (OI) opportunities now extend to individuals with creative ideas and interests in innovation. Understanding why individuals are willing to engage in open innovation and how their diverse goals affect their participation is important for assessing the viability of various OI models and to inform platform design. In this paper, we develop a theoretical model that examines the impact of three categories of human goals––extrinsic, intrinsic and internalized extrinsic––on actors’ continuous intentions to participate in three general categories of open innovation behaviors––ideation, collaboration and socialization. The model also considers how perceived platform participation affordances mediate the influence of goals on these innovation behaviors. We validate this goals-affordances-behavior model via a field survey of participants on a Social Product Development (SPD) platform. By theorizing and empirically examining how goals influence participation in the SPD context, our study advances knowledge about open innovation behaviors, provides a foundation for future research across various OI models, and highlights practical insights for OI platform design.