Abstract Background Mental health in adolescence is an increasing global public health concern. Over half of all mental disorders debut by 14 years of age and remain largely untreated up to adulthood, underlining the significance of early detection. The study aimed to investigate whether parental distress rating at the child’s age of 15 predicts a probable mental diagnosis in a three-year follow-up. Methods All data was derived from the Finnish Family Competence (FFC) Study. The analysis focused on whether parental CBCL (Child Behavior Checklist) rating (n = 441) at the child’s age of 15 years predicted the outcome of the child’s standardised DAWBA (Development and Well-Being Assessment) interview at offspring’s 18 years. Results Multivariable analysis showed that a one-unit increase in the total CBCL scores increased the relative risk of a DAWBA-based diagnosis by 3% (RR [95% CI] 1.03 [1.02–1.04], p < 0.001). Conclusions Parental CBCL rating in a community sample at the adolescent’s age of 15 contributes to early identification of adolescents potentially at risk and thus benefitting from early interventions.