This study aimed to investigate prospectively the contribution of maternal physical health and/or breastfeeding problems to maternal mood (depression, anxiety, fatigue, irritability, confusion, vigor) at 8-weeks postpartum. A prospective study was conducted. Participants were recruited antenatally from a public and a private maternity hospital in Melbourne, Australia. Nulliparous pregnant women (N = 229), ≥ 18 years of age, ≥ 36-week gestation, singleton pregnancy and with sufficient English were eligible. Data were collected by self-report questionnaire (pregnancy, weeks 1-4 postpartum) and telephone interview (week 8 postpartum). A high burden of physical problems was classified as ≥ 3 problems (caesarean/perineal pain; back pain; constipation; haemorrhoids; urinary and bowel incontinence) for ≥ 2 time points. A high burden of breastfeeding problems was having ≥ 2 problems (mastitis; nipple pain; frequent expressing; over- or under-supply of milk) for ≥ 2 time points. Multivariate linear regression was used to investigate the relationship between maternal mood, assessed using Profile of Mood States (8-week postpartum), and a high burden of breastfeeding and/or physical health problems. Forty-six women (20.1%) had a high burden of physical symptoms, 44 (19.2%) a high burden of breastfeeding problems only and 25 women (11.0%) had both. A high burden of breastfeeding problems alone (β = 10.6, p = 0.01) or with co-morbid physical problems (β = 15.35, p = 0.002) was significantly associated with poorer maternal mood at 8 weeks. Early, effective postnatal treatment of maternal health and breastfeeding problems could reduce women's risk for poor mental health.