This paper uses discourse theory to obtain a broader understanding of how research impact of sustainable tourism research develops in the environmental policy domain. Discourse theory shifts emphasis from the substance of science versus policy to the use of science in policy processes and explains the political dimensions of policymaking. We first review a well-documented science-policy gap in sustainable tourism research on climate change to develop an alternative conceptualisation of research impact. Then, using a case study approach, we investigate this framework by evaluating the impact of a PhD thesis about aviation’s global CO2 emissions on the Dutch aviation policy process. The case study shows research impact is entwined with various other elements, and embedded in a specific governance context. Research influenced contrasting science-policy interactions and contributed to conflicting policy actions and reactions. The impact of research in this case was manifested through the formation and interplay of multiple knowledge objects that were both embraced and marginalised. In settings like this, research is used to legitimise pre-existing policy positions rather than to develop new policies. We discuss the implications of narrow conceptions of research impact. The paper highlights the need for advanced policy analysis in sustainable tourism research.