Approximately 15% of new mothers experience postpartum depression, representing the most common source of maternal morbidity post-delivery. Postpartum depression may impair maternal–infant interactions, contributing to poor developmental outcomes in the offspring of mothers with depression. The purpose of this study was to test the effectiveness of home-based peer support that included maternal–infant interaction teaching for mothers with symptoms of postpartum depression and their infants. Mothers with postpartum depression were randomly assigned to control (n = 33) or intervention groups (n = 27). Intervention group mothers received 12 weeks of home-based peer support that included maternal–infant interaction teaching; peers were mothers who had recovered from postpartum depression and were trained to provide support. Data were collected from all mothers at baseline, as well as 6 and 12 weeks' post-randomization. Contrary to the hypothesized direction of relationships, results favoured the control group. A significant difference between the groups was observed for one of the two measures of maternal–infant interactions. Several other measures favoured the control group, including mothers' depressive symptoms and social support scores. No significant treatment effects were observed in infant IQ scores or diurnal salivary cortisol levels in mothers or infants. The findings suggest that maternal–infant interaction teaching by peers is not well received by mothers with postpartum depression and might be more optimally delivered by professional nurses.