Background: Poor perinatal maternal mental health has been linked with negative outcomes on early child development; however, the importance of maternal personality has been neglected thus far. We aimed to examine the effects of antenatal and postnatal maternal mental health, including assessment of maternal personality characteristics, on child neuropsychological and behavioral development at preschool years in a population based mother-child cohort (Rhea Study) in Crete, Greece. Method: Self-reported measures of maternal depression (EPDS), trait anxiety (STAI-Trait) and personality traits (EPQ-R) were assessed in a sample of 288 women at 28-32 weeks of gestation. A larger sample of 642 mothers completed the EPDS scale at 8 weeks postpartum. Children’s neuropsychological (MSCA) and behavioral (ADHDT and SDQ) development were assessed at 4 years of age. Linear regression analyses were used to estimate the associations between the exposures and outcomes of interest after adjustment for potential confounders. Results: Regarding child neuropsychological development, increased postnatal depressive symptoms were associated with child’s perceptual performance, whereas increased maternal psychoticism was linked with child’s motor ability at 4 years of age. Furthermore, elevated levels of maternal depression during pregnancy and postpartum, and the predisposing personality characteristics of trait anxiety and neuroticism, were associated with children’s behavioral difficulties. Limitations: A clinical diagnostic instrument for maternal mental health was not used and assessment of children’s behavior was based on maternal report. Conclusion: These findings suggest that poor perinatal maternal mental health and an adverse personality profile may be associated with impaired child neuropsychological and behavioral development at preschool years.