In this contribution, we put the spotlight on the interlinkages between participatory knowledge production and sustainabili ty transformations by proposing an empirical enquiry into transdisciplinary (TD) research projects. With regard to (un)sustainab le development the limitations of knowledge production within the exclusive realms of science have become manifest in malfunc- tio ning feedback between science and political action. In reaction, claims have been made that scientific inquiry along clear -cut boundaries between scientific knowledge production and the societal usage thereof is not sufficient for tackling complex sust ain- ability problems. TD, which aims at integrating heterogeneous actors and diverse forms of expertise, has emerged as a key noti on in this quest for more “robust?” and responsive knowledge. One core assumption in the literature is that the participation of a wider set of societal actors enhances the societal impact of research and facilitates transformations. In this presentation, we juxtapose this assumption with meta -level reflections on real -world TD sustainability research cases. We investigate (i) which factors constitute different practices of participation, (ii) how actors in TD projects establish the link between participati on prac- tices and intended societal impact of their projects and (iii) which other influence factors they perceive as relevant for t heir in- tended societal impacts. In doing so, we look at a sample of sustainability research projects funded by the program “Science for Sustainable Development (WfNE)” of the Ministry for Science and Culture of Lower Saxony and the Volkswagen Foundation. T hese projects represent a broad variety of topics and research designs including diverse participatory approaches and intended soc ie- tal effects. Our results are based on a series of qualitative analyses: We performed a document analysis of the project prop osals and two rounds of interviews with project leaders and scientists. Furthermore, we included the practice perspective in our an aly- sis by conducting interviews with non -scientific actors involved in the projects. This procedure allows us to provide find ings on how both scientific and non -scientific actors in TD projects in the field of sustainability research conceive of and perceive (i) par- ticipation processes in the project, (ii) participation as an influence factor for societal impacts, and (iii) furt her project- or con- text -based influence factors for the intended societal effects. Finally, we present a tentative analytical framework sensitive to diverse participatory processes and different types of potential impacts they are associated with.