While the importance of transdisciplinary (Td) processes as a means to address societal problems is well-established, guidance for the intentional design of stakeholder interactions to meet specific goals, under different conditions and contexts, remains less explored. We propose the concept of critical design moments (CDMs) as a lens through which to identify key processes in the design of stakeholder interactions that affect the relevance and impact of its outcomes. We demonstrate how an approach using CDMs can help to make explicit not only the goals of stakeholder interactions, but also how these goals might be met through the process design of specific activities orienting these interactions. The CDMs were identified as part of the implementation of a Td winter school for early career researchers to provide them with real-world experiences of interacting with stakeholders and local residents of a community. This work provides an approach for how Td stakeholder interactions can be designed in other Td contexts.