Background: Empirical studies have revealed a significant, but modest association between maternal depression and insecure mother-child attachment. Across studies, however, a substantial number of mothers with depression are able to provide a sensitive caretaking environment for their children. This paper aimed to explore whether a mother's own state of mind regarding attachment moderated the association between postpartum depression and insecure mother-child attachment. Methods: Mothers (n = 111), mainly middle-class mothers, and their infants participated in a longitudinal study of postnatal depression, maternal attachment state of mind and child attachment. Depression was assessed using a diagnostic interview (at 4 and 12 months) and symptom checklists (at 4, 12 and 15 months). The Adult Attachment Interview was conducted at 12 months and the Strange Situation procedure at 15 months. Results: Mothers diagnosed as depressed were more likely to have an insecure state of mind regarding attachment. Infants of chronically depressed mothers were more likely to be insecurely attached; however, the relationship between maternal depression and child attachment was moderated by maternal attachment state of mind. Conclusions: Results are discussed with reference to resiliency factors for women with postnatal depression and implications for intervention.