This study explores how mobile and immobile academics enact research collaborations in Centres of Excellence (CoEs) in the Social Sciences and Humanities (SSH). Modelled on Big Sciences and underpinned by human capital assumptions, CoEs aim to foster both local and international collaborations, driven by academic mobilities. Based on critical approaches to mobilities, this study presents a nuanced analysis that challenges the idealisation of mobility and its assumed positive impacts on collaboration. The findings reveal distinct logics of collaboration: immobile academics engage in constructive local collaborations that foster multidisciplinary research, and they emphasise the significance of international collaborations for both individual and collective disciplinary advancements. Mobile academics, in contrast, are largely excluded from local collaborations and their most meaningful collaborations occur internationally, whilst they depict the CoE as parochial. The study situates these dynamics within broader tensions between policy expectations and the uniqueness of academic practices in the field of the SSH.