Sexual and gender minorities (SGM) include individuals with a wide range of sexual orientations, physical characteristics, and gender identities and expressions. Data suggest that people in this group face a significant and poorly understood set of additional health risks and bear a higher burden of some diseases compared to the general population. A large amount of data is available on HIV/AIDS, but far less on other health problems. In this review we aimed to synthesize the knowledge on the burden of communicable and non-communicable diseases, mental health conditions and violence experienced by SGM, based on available systematic reviews. We conducted a global review of systematic reviews, including searching the Cochrane and the Campbell Collaboration libraries, as well as PubMed, using a range of search terms describing the populations of interest, without time or language restrictions. Google Scholar was also scanned for unpublished literature, and references of all selected reviews were checked to identify further relevant articles. We found 30 systematic reviews, all originally written in English. Nine reviews provided data on HIV, 12 on other sexually transmitted infections (STIs), 4 on cancer, 4 on violence and 3 on mental health and substance use. A quantitative meta-analysis was not possible. The findings are presented in a narrative format. Our review primarily showed that there is a high burden of disease for certain subpopulations of SGM in HIV, STIs, STI-related cancers and mental health conditions, and that they also face high rates of violence. Secondly, our review revealed many knowledge gaps. Those gaps partly stem from a lack of original research, but there is an equally urgent need to conduct systematic and literature reviews to assess what we already know on the disease burden in SGM. Additional reviews are needed on the non-biological factors that could contribute to the higher disease burden. In addition, to provide universal access to health-care for all, more information is needed on the barriers that SGM face in accessing health services, including the attitudes of health-care providers. Understanding these barriers and the additional health risks they impose is crucial to improving the health status of SGM.