Postpartum depression (PPD) is a condition that affects about 10% of newly delivered women. The aim of this study was to examine the possible association between offspring gender and risk for development of PPD in Sweden. The study was undertaken as part of the UPPSAT project, a population-based longitudinal study in Uppsala, Sweden. From May 2006 to June 2007, women who gave birth at Uppsala University Hospital and fulfilled the inclusion criteria were asked to participate. The participating women filled out, at three points during the first 6 months after delivery, questionnaires containing the Edinburgh Postnatal Depression Scale as well as questions concerning various lifestyle factors, medical history, breast feeding habits, social support parameters, and diet factors. No significant difference in risk of PPD in relation to baby gender could be shown 6 weeks and 6 months after delivery. However, women who gave birth to a male offspring had a significantly higher risk of self-reported depressive symptomatology 5 days after delivery. The association remained statistically significant after adjustment for possible confounders in a logistic regression model. This longitudinal study demonstrates that, in Sweden, the gender of the offspring is not associated with a higher risk for self-reported postpartum depression in the mother 6 weeks or 6 months after delivery. The birth of a baby boy, however, gives the mother a higher risk of postpartum blues 5 days after delivery.