Background Much postpartum physical and psychological morbidity is not addressed by present care, which tends to focus on routine examinations. We undertook a cluster randomised controlled trial to assess community postnatal care that has been redesigned to identify and manage individual needs. Methods We randomly allocated 36 general practice clusters from the West Midlands health region of the UK to intervention (n=17) or control (19) care. Midwives from the practices recruited women and provided care. 1087 (53%) of 2064 women were in practices randomly assigned to the intervention group, with 977 (47%) women in practices assigned to the control group. Care was led by midwives, with no routine contact with general practitioners, and was extended to 3 months. Midwives used symptom checklists and the Edinburgh postnatal depression scale (EPDS) to identify health needs and guidelines for the management of these needs. Primary outcomes at 4 months were obtained by postal questionnaire and included the women's short form 36 physical (PCS) and mental (MCS) component summary scores and the EPDS. Secondary outcomes were women's views about care. Multilevel analysis accounted for possible cluster effects. Findings 801 (77%) of 1087 women in the intervention group and 702 (76%) of 977 controls responded at 4 months. Women's mental health measures were significantly better in the intervention group (MCS, 3.03 [95% CI 1.53-4.52]; EPDS -1.92 [-2.55 to -1.29]; EPDS 13+ odds ratio 0.57 [0.43-0.76]) than in controls, but the physical health score did not differ. Interpretation Redesign of care so that it is midwife-led, flexible, and tailored to needs, could help to improve women's mental health and reduce probable depression at 4 months' postpartum.