This contribution puts the spotlight on participation of heterogeneous actors and diverse forms of expertise in knowledge production and its implications for governance of complex problems. With regard to tackling complex ‘global’ problems, multifaceted debates about the interlinkages between science and policy have gained momentum. A ‘participatory turn’ (Jasanoff 2003) in both the governance and practice of science has been observed and notions such as ‘politicisation of science’ (Weingart 1983) have been brought forward. In particular, with regard to (un)sustainability, malfunctioning feedback between science and political action has triggered debates on the limitations of knowledge production within the exclusive realms of science. In reaction to the diagnosis of a sobering impact of science on societal change, the European Commission and other funding bodies have been calling for the integration of non-scientific actors and expertise into the production of allegedly more responsive knowledge. Despite this widespread call for a transgression of science-society boundaries, critical theoretical reflections on the meanings and practices of participation in different scientific and political contexts are scant. This contribution asks which factors constitute and shape practices of participation in knowledge production. By means of a review of empirical and case study-based literature in the field of Science and Technology Studies, development research and sustainability research (i) underlying understandings of democratic processes and implicit assumptions on science-policy relations are critically reflected and (ii) the role of institutional (e.g. scientific reward structures), structural (e.g. resources) and actor-based factors (e.g. mutual trust) in the making of participation at the science–policy interface is examined.