PurposeThe concept of open innovation has captured the attention of both academics and practitioners alike. However, there is a dearth of research on how innovations can be diffused within open innovation ecosystems, a critical condition for the sustainability of such ecosystems. In this regard, the study advances a research agenda for guiding future inquiries into innovation diffusion within open innovation ecosystems.Design/methodology/approachBased on a systematic review of the extant literature on open innovation, this article identifies knowledge gaps in innovation diffusion, along with recommendations for bridging these gaps in the future. The study advocates that future research should consider not only innovation generation processes, but also innovation diffusion processes, especially in light of the growing application of open innovation in the context of digital goods and services.FindingsSubscribing to an evolutionary view of innovation diffusion, the article draws on a five-phase framework – knowledge, persuasion, decision, implementation, and confirmation – to illustrate the roles played by three distinct yet interconnected parties (i.e. platforms, complementors, and individuals) within open innovation ecosystems as well as the research opportunities it brings.Originality/valueThe article examines the critical, yet underexplored role of innovation diffusion in sustaining open innovation ecosystems and outlines potential research avenues that can contribute to growing the understanding of the innovation diffusion process.