Children exposed to maternal depression during pregnancy and in the postnatal period are at increased risk of a range of health, wellbeing and development problems. However, few studies have examined the course of maternal depressive symptoms in the perinatal period and beyond on children's wellbeing. The present study aimed to explore the relationship between both the severity and chronicity of maternal depressive symptoms across the early childhood period and children's emotional-behavioural difficulties at 4 years of age. Data from over 1,085 mothers and children participating in a large Australian prospective pregnancy cohort were used. Latent class analysis identified three distinct trajectories of maternal depressive symptoms from pregnancy to 4 years postpartum: (1) no or few symptoms (61%), (2) persistent subclinical symptoms (30%), and (3) increasing and persistently high symptoms (9%). Regression analyses revealed that children of mothers experiencing subclinical and increasing and persistently high symptoms were at least two times more likely to have emotional-behavioural difficulties than children of mothers reporting minimal symptoms, even after accounting for known risk factors for poor outcomes for children. These findings challenge policy makers and health professionals to consider how they can tailor care and support to mothers experiencing a broader spectrum of depressive symptoms across the early childhood period, to maximize opportunities to improve both short-and long-term maternal and child health outcomes.