Abstract Introduction Studies that examine the mental health of gay, lesbian, and bisexual (LGB) older adults have increased significantly over the last two decades, evidencing sexual stigma as one of the main factors associated with poorer mental health in this population. However, scientific evidence linking mental health and sexual stigma in older adults has not been systematically reviewed. Methods We conducted a systematic scoping review investigating the relationships between sexual stigma and mental health in LGB older adults aged 60 and over. EBSCO Host, PubMed, Web of Science, Scopus, and Scielo were used to search for peer reviewed studies following PRISMA guidelines and 17 studies were included. The research covered studies between 2000 and 2020 and data collection was carried out between 2020 and 2021. Results Sexual stigma showed a strong relationship with mental health in LGB older adults, being mainly associated with worse mental health outcomes, such as anxious and depressive symptoms, psychological distress, and substance abuse. Hypervigilance, invisibility, feeling socially rejected, concealment of sexual orientation, and internal conflicts were suggested among the main mediator/moderator factors between sexual stigma(s) and the older LGB mental health indicators. The findings suggest that sexual stigma affects older LGB people throughout their life course cumulatively, by decreasing their quality of life and access to health care. Yet, LGB older adults have developed resilience and adaptive strategies to manage sexual stigma. Conclusions and Policy Implications Sexual stigma has a significant relationship with worse levels of mental health in LGB older adults, affecting their well-being. It is important that future studies address oldest old LGB individuals (e.g., aged 80 or over), particularly evaluating how they manage sexual stigma. Further, there is an urgent need for research that evaluates the positive determinants of mental health in LGB older adults, such as well-being and successful aging, as well the role of the internet and social media in stigmatizing older LGB people.