BACKGROUND Prior studies providing estimates of the prevalence of postnatal depressive symptoms (PNDS) in New Zealand have been hampered by methodological shortcomings. Aims of this study were to derive an accurate estimate of PNDS prevalence and treatment frequency in an urban population of a major city in New Zealand. METHOD This was a one-wave postal survey of a probability, community sample of all women in Auckland who were 4 months postpartum. PNDS was assessed with the Edinburgh Postnatal Depression Scale (EPDS). RESULTS There were 225 usable responses (78% response-rate): 36 women (16.0%) scored above the threshold for depressive symptomatology, and nine of them were in treatment. A further 31 women (13.8%) scored just below the threshold region for depressive symptomatology, and none were in treatment. CONCLUSION The prevalence rate of PNDS in urban New Zealand is slightly higher than the world-wide average, and goes largely untreated in the community. Health care providers should remain vigilant to the finding that almost one in three mothers with infants is suffering with symptoms of depression and may need strong encouragement to admit they need help.