Policy increasingly requires societally relevant and interdisciplinary science, which prompts questions about science’s orientation to diverse academic and non-academic actors. This paper examines how relevance is practised and negotiated in two evolving interdisciplinary social science fields: marine social sciences and forest policy research. Both fields investigate human relations with specific environments: how people use, manage and govern, live with and value seas and forests. Diverse social and political actors have stakes in the knowledge these fields generate. To whose matters and stakes do researchers respond and orient their research? Are such orientations reflexively discussed and contested? To operationalise relevance, we employ the notion of ‘epistemic commitments’ while adopting a Bourdieusian perspective on scientific fields. Our analysis draws on conference observation, interviews and document analysis. We find diverse epistemic commitments in both fields, but see noticeable differences in their prevalence, reflexivity and contestation. Examining the fields’ socio-historical trajectories, we theorise that these differences are due to field-specific properties: their relative autonomy to negotiate relevance independently from other disciplines and external forces; and the field-specific habitus that impacts the degree to which relevance is a reflexive commitment, or an unconscious practice. The comparative analysis suggests that interdisciplinary scientific fields’ specific institutional histories and relations with societal and policy actors shape relevance practices and the extent to which these are internally contested.