Objective: This study examined the relationship between maternal postnatal depression (PND) at 6 weeks and first-year parenting stress for mothers of very preterm (gestation < 32 weeks) singleton children. Background: PND is reported as a strong predictor of parenting stress, but few studies examine the effectiveness of parenting interventions according to PND status. In the preterm population, the differential benefit mothers with PND experience from parenting interventions is also unclear. Methods: Validated questionnaires were used to collect information on both PND at 6 weeks and first-year parenting stress from 123 mothers of very preterm singleton children. Results: After adjusting for baseline birth and social risks, mothers who had PND at 6 weeks were more likely to experience parenting stress (OR 3.6, 95%CI 1.2, 12, p = 0.03) and have higher parental distress (OR 5.5, 95%CI 1.6, 18.0, p < 0.01) during the first postpartum year. Conclusion: When assessing the benefits of parenting interventions in reducing parenting stress, the effects of early PND in mothers of preterm infants should not be underestimated.