Maternal experience of child maltreatment (CM) has been associated with maternal and child mental health. However, evidence about the course of child mental health and maternal CM is scarce. Therefore, this study aims to compare trajectories of mental health in children according to maternal CM exposure and maternal mental health. We included 327 mothers and their singleton child from the Ulm SPATZ Health Study, a prospective birth cohort study. Child mental health was determined by the Strength and Difficulties Questionnaire (SDQ) at the age of 4, 5, 6, and 7 years and maternal CM by the Childhood Trauma Questionnaire (CTQ). Results display that maternal CM is associated with more behavioural and emotional difficulties in children, a trend that tends to increase with older child age. The sum of maternal mental health problems across this time course mediates this association. Male child sex is associated with more mental health problems in the child and the mother. These results provide an important first insight into the relevance of maternal CM on the trajectories of mental health in the offspring and highlight the importance of chronicity and severity of maternal mental health. Further prospective research in cohorts with longer follow-ups up into adolescence and adulthood is needed.