An emerging body of evidence suggests that intergenerational sexual partnerships may increase risk of HIV acquisition among young men who have sex with men (YMSM). However, no studies have comprehensively evaluated literature in this area. We applied a scoping review methodology to explore the relationships between age mixing, HIV risk behavior, and HIV seroconversion among YMSM. This study identified several individual, micro-, and meso-system factors influencing HIV risk among YMSM in the context of intergenerational relationships: childhood maltreatment, coming of age and sexual identity, and substance use (individual-level factors); family and social support, partner characteristics, intimate partner violence, connectedness to gay community (micro-system factors); and race/ethnicity, economic disparity, and use of the Internet (meso-system factors). These thematic groups can be used to frame future research on the role of age-discrepant relationships on HIV risk among YMSM, and to enhance public health HIV education and prevention strategies targeting this vulnerable population.