Collaborative science has become a ‘gold standard’ in sustainability science, to address increasingly complex socio-environmental challenges and knowledge divides. Inequalities shaping research collaborations (RCs) however remain unexplored in the science-policy interface. To address this gap, we carry out a critical discourse analysis of texts by international policy and research actors engaged in the global discourse on science for sustainability. We examine which narratives of RC they mediate, and how these address inequalities related to RC. Our study shows that documents of United Nations bodies primarily mediate a deficit narrative, with focus on a lack of resources and innovation capacity in ‘less developed’ countries. The alternative transformation narrative of RC mediated by reports of UNESCO and other science-policy institutions implementing science for the SDGs offers a more complex picture, which accounts for epistemic inequalities and frames RC as essential to address global challenges. The latter narrative holds most potential for change yet emerges with a varying prevalence, which we explain by institutional contexts and disciplinary diversity of experts. We find a disparity in the visibility of the transformation narrative in texts by policy actors and academic actors implementing science for sustainability. This may have structural implications for RC in global science and the inequalities they (re-)produce or counter. We suggest a more nuanced engagement with RC as policy and research subject for science to deliver the holistic transformation the 2030 Agenda strives for.