There is evidence that psychological treatments for postnatal depression are effective in the short-term; however, whether the effects are enduring over time remains an important empirical question. The aim of this study was to investigate the depressive symptoms and interpersonal functioning of participants in a randomised controlled trial (RCT) of group interpersonal psychotherapy (IPT-G) at 2 years posttreatment. The study also examined long-term trajectories, such as whether participants maintained their recovery status, achieved later recovery, recurrence or persistent symptoms. Approximately 2 years posttreatment, all women in the original RCT (N = 50) were invited to participate in a mailed follow-up. A repeated measures analysis of variance assessed differences between the treatment and control conditions on depression and interpersonal scores across five measurement occasions: baseline, mid-treatment, end of treatment and 3-month and 2-year follow-up. Chi-square tests were used to analyse the percentage of participants in the four recovery categories. Mothers who received IPT-G improved more rapidly in the short-term and were less likely to develop persistent depressive symptoms in the long-term. Fifty seven percent of IPT-G mothers maintained their recovery over the follow-up period. Overall, IPT-G participants were significantly less likely to require follow-up treatment. Limitations include the use of self-report questionnaires to classify recovery. The positive finding that fewer women in the group condition experienced a persistent course of depression highlights its possible enduring effects after treatment discontinuation. Further research is needed to improve our long-term management of postnatal depression for individuals who are vulnerable to a recurrent or chronic trajectory.