The present research points to an alternative concern against the mainstream research of future ports’ development by taking a transdisciplinary approach of a Living Lab (LL) concept for a better sustainability and innovation record in Small and Medium-Sized Ports (SMSPs). Deploying qualitative research for the examination of this new phenomenon of aggregating LLs into SMSPs, this research builds upon stakeholder workshops, in-depth interviews, and designed port pilots as case studies dedicated to innovation and sustainability transition in the Baltic Sea Region (BSR) at the turn of 2030. Given its rich and significant empirical foundation, the present research substantially contributes to sustainability orientation and transitions in ports. The key original elements of this study are fourfold: (1) the research provides a theoretical and practical LL framework enabling innovation and sustainability to be grasped in ports in times of technological, social, and political disruption; (2) this research increases the minimal number of existing previous efforts studying SMSPs in the transitional discourse; (3) the paper addresses not only hard technological innovation concerns but also aspects of social acceptance and the role of social interactions; (4) the research goes beyond geographical boundaries of a single port, thus providing a joint and collaborative approach towards sustainability rather than an individual perception on sustainability transition, existing networks, and clusters. © 2024 by the authors.