Despite growing concern about mental health problems in university students and increasing recognition that first-generation university students (FGS) may face additional challenges, there has been no previous attempt to map the existing research on FGS mental health. The aim of this scoping review was to elicit current understanding of mental health problems in FGS from the literature. Following database searches and screening, 40 peer-reviewed articles were included in the scoping review. Findings from these studies were synthesised for: types of mental health problems in FGS; prevalence of mental health problems in FGS compared to continuing-generation students (CGS); factors associated with mental health problems in FGS; effects of mental health problems on FGS; help-seeking for mental health problems in FGS; and interventions. Significant gaps were highlighted and recommendations made for future research, particularly outside the United States. True commitment to widening participation demands much more research on mental health problems in FGS to ensure that they thrive not just arrive.