The literature on the lived experiences of early-career researchers (ECRs) has not fully leveraged the analytical potential of the concepts of 'sponsorship' and 'gatekeeping' when examining the importance of senior scholars in their work lives. This article conceptualises the micro-politics of seniors' sponsorship of ECRs based on 19 semi-structured interviews and two focus groups at a Danish university. Sponsorship can take the forms of co-authoring, creating network contacts, or securing funding. The micro-politics of sponsorship enable seniors to mobilise opportunities for juniors, often at the 'backstage' of academia. Sponsorship strengthens the interviewees' feelings of job-related security, but not all ECRs are sponsored. According to the interviewees, sponsorship relationships develop for academic reasons, such as shared research interests, but are also a matter of luck, personal chemistry, and 'homophily', leading to subtle processes of inclusion and exclusion in academia. Regardless, sponsorship is widely considered a taken-for-granted, legitimised practice.