This article investigates the role of socioeconomic family resources in modifying the relationships with upper secondary school completion (SSC) for three mental health dimensions, i.e., externalizing, internalizing and substance use disorders. Using data from administrative registers, we follow a cohort in Norway born in 1996 into early adulthood. We find that having a mental health disorder in adolescence was associated with 12-17 percentage points lower SSC rate after adjustment for demographic and household factors, comorbidity and educational performance. In girls, high family income attenuated the negative relationships between all three mental health dimensions and SSC, while in boys, this was true only for substance use disorders. The paper concludes that access to family socioeconomic resources "buffers" the negative impact of mental health disorders on SSC, but less so in boys, contributing to aggravate social and health-related inequalities in SSC.