Background Young adults at work without basic educational level (BEL), and young adults in Neither Employment, Education nor Training (NEET) are at high risk of adverse employment outcomes. Evidence lacks on the impact of mental health problems during childhood, adolescence and young adulthood on employment outcomes of young adults. Therefore, the aims of this study were to (1) identify trajectories of mental health problems from childhood to young adulthood and (2) investigate the relation between these trajectories and the educational or employment status of young adults. Methods Data were used from the Tracking Adolescents' Individual Lives Survey (TRAILS), a Dutch prospective cohort study with 9-year follow-up. Trajectories of mental health problems measured at ages 11, 13.5, 16 and 19 years were identified in 1711 young adults with latent class growth models. Results Young adults with high-stable trajectories of total problems, from childhood to young adulthood, were more likely to work without BEL or be in NEET at age 19, than to be at school or to work with BEL (28.0% vs 16.0%, p=0.01). The same was found for externalising problems (35.3% vs 23.2%, p=0.02). For internalising and attention problems, no statistically significant differences were found. Conclusions Young adults with high-stable trajectories of mental health problems from age 11 to 19, were at risk of adverse employment outcomes. Interventions reducing mental health problems in childhood may improve the educational or employment status of young adults and their chances for successfully entering the labour market.