OBJECTIVES: In this narrative review we illustrate the patterns of substance use among gay, bisexual and other men who have sex with men (MSM), including comparisons with heterosexual populations, subgroup analyses and settings of substance use. We also consider explanations and motivations for substance use and the impact of use on sexual health as well as wider health and well-being. Finally, we consider the implications for the provision of MSM-tailored substance use and harm reduction services. METHODS: We undertook a narrative review of diverse literature across the fields of public health, psychology and sociology to synthesise complex findings relating to the use and impacts of illicit drugs and alcohol among MSM. Attempts were made to draw on literature from across the globe, including all income settings. RESULTS: Global evidence relating to the use of substances among MSM is limited due to the lack of disaggregation of data by sexual orientation. While complicated by methodological diversity, most research indicates a higher prevalence of illicit drug use among MSM compared with their heterosexual counterparts, although the same is not necessarily true of alcohol. A sense of belonging, coping with everyday problems and the enhancement of pleasure, all feature in motivations for alcohol and drug use. Global association studies document a link between substance use and sexual risk behaviours, and event-level analyses suggest an especially strong association with respect to alcohol. While there is some evidence that generic harm reduction interventions can be effective among sexual minorities, these need to be tailored to the social and cultural circumstances of MSM. CONCLUSIONS: Associations between substance use and sexual risk behaviour among MSM have been well documented, but the nature and pathway of these are poorly understood. A focus largely on substance use and sexual risk may have served to mask the impact of alcohol and drug use on the broader health and well-being of MSM.