Early parenting services in Australia offer brief structured residential programs to address moderate to severe non-psychotic mental health problems among women and unsettled infant/toddler behaviours. The aims were to (1) estimate the immediate and medium-term impact of a five-night psychoeducational residential early parenting program on postpartum depressive symptoms and (2) identify the factors associated with improvement or worsening of postpartum depressive symptoms after completing the program and six weeks post-discharge. Audit of routinely collected medical record data from pre-admission, pre-discharge and post-discharge assessments of a consecutive cohort of women admitted, with their infants/toddlers in a 15-month period to Masada Private Hospital Early Parenting Centre. Data included structured questions assessing: demographic characteristics, access to family and social support, past and current mental health problems, reproductive and obstetric health, chronic health conditions, breastfeeding problems, coincidental major life events, health risk behaviours and infant/toddler feeding, sleeping and crying behaviours. Standardised instruments included the Partner Interaction after Birth Scale (PIBS), the MacLean Screening Instrument for Borderline Personality Disorder (MSI-BPD), Modified Fatigue Assessment Scale (FAS) and selected items from the Karitane Parenting Confidence Scale. The primary outcomes were Edinburgh Postnatal Depression Scale scores at pre-discharge and follow up assessments. Data were analysed using multinomial logistic regression models in which individual and psychosocial characteristics at pre-admission were included as predictors of the likelihood of the changes of the outcomes from pre-admission to pre-discharge and follow up. Complete data from 1220 of 1290 (95%) eligible women were available to assess pre-admission to pre-discharge and from 559 (45.8%) to assess pre-discharge to six-week follow-up changes. The mean pre-admission EPDS score was 11.7 (95% CI: 11.5; 12.0), pre-discharge it was 7.1 (95% CI: 6.9; 7.4) and at six-week follow up it was 5.7 (95% CI: 5.3; 6.1). We found that almost all women experienced a clinically meaningful and rapid improvement in depressive symptoms of at least this magnitude (reduction in mean EPDS scores of 4.6 points from pre-admission to pre-discharge (five nights) and a further reduction of 1.2 points pre-discharge to follow up) (six weeks) and we identified an interpretable set of risk factors for symptoms that did not improve or worsened. The adverse outcomes were associated with having symptoms of borderline personality disorder, a partner experienced as lacking kindness and care, coincidental adverse events and having a child younger than six months. Residential early parenting programs, which take a psycho-educational approach to strengthening caregiving skills, maximising agency, and reducing helplessness, have a rapid beneficial effect on women's postpartum depressive symptoms. These programs provide a valuable and effective component of comprehensive mental health services. Long-term dialectical behaviour therapy is indicated for women with borderline personality disorder traits for whom early parenting programs alone are insufficient to improve depressive symptoms.