Background Studies have shown a link between maternal–prenatal mental health and offspring behavior problems. In this paper, we derived longitudinal trajectories of maternal depressive, anxious, and stress symptoms over early life to predict offspring behavior in adolescence. Methods Participants included 3,925 mother–offspring pairs from the Mater University Study of Pregnancy (MUSP), an Australian‐based, prebirth cohort study. Latent class growth analysis with parallel processes was used to identify trajectories of maternal depressive, anxious, and stress symptoms over four measurement periods between the mothers’ first clinic visit and 5 years postpregnancy. The estimates from the maternal trajectories were used to fit multivariate logistic regression models and predict internalizing and externalizing behavior at age 14. We adjusted for a wide range of factors, including a number of prenatal confounders, concurrent maternal depressive and anxious symptoms, father's history of mental problems, and maternal life events relationship quality and contact with the new born. Results Seven maternal trajectories were identified one of which isolated high levels of depressive, anxious, and stress symptoms during pregnancy. After adjustment for confounders, this was the only trajectory that predicted higher internalizing behavior in adolescence. No specific maternal trajectory predicted externalizing problems. Conclusions We found evidence for a prenatal effect, whereby high levels of maternal depression, anxiety, and stress symptoms in early pregnancy uniquely increased the risk of internalizing behavior problems in adolescence.