Transdiagnostic frameworks posit a causal link between emotion regulation (ER) ability and psychopathology. However, there is little supporting longitudinal evidence for such frameworks. Among N = 1,262 adolescents, we examined the prospective bidirectional relationship between ER and future pathological anxiety, depression, and substance dependence symptoms in 10 assessment waves over 7 years. In Random-intercept cross-lagged panel models, within-person results do not reveal prospective lag-1 effects of either ER or symptoms. However, between-person analyses showed that dispositional ER ability at baseline predicted greater risk for developing clinically significant depression, anxiety, and substance dependence over the 7-year follow-up period. These findings provide some of the first direct evidence of prospective effects of ER on future symptom risk across affect-related disorders, and should strengthen existing claims that ER ability represents a key transdiagnostic risk factor.