conflict in low-income and middle-income countries, yet few scalable options for their mental health care exist. We aimed to establish the effectiveness of a brief group psychological intervention for women in a conflict-affected setting in rural Swat, Pakistan. METHODS: In a single-blind, cluster, randomised, controlled trial, 34 community clusters in two union councils of rural Swat, Pakistan, were randomised using block permutation at a 1:1 ratio to intervention (group intervention with five sessions incorporating behavioural strategies facilitated by non-specialists) or control (enhanced usual care) groups. Researchers responsible for identifying participants, obtaining consent, enrolment, and outcome assessments were masked to allocation. A community cluster was defined as neighbourhood of about 150 households covered by a lady health worker. Women aged 18-60 years who provided written informed consent, resided in the participating cluster catchment areas, scored at least 3 on the General Health Questionnaire-12, and at least 17 on the WHO Disability Assessment Schedule were recruited. The primary outcome, combined anxiety and depression symptoms, was measured 3 months after the intervention with the Hospital Anxiety and Depression Scale (HADS). Modified intention-to-treat analyses were done using mixed models adjusted for covariates and clusters defined a priori. The trial is registered with the Australian New Zealand Clinical Trials Registry, number 12616000037404, and is now closed to new participants. FINDINGS: From 34 eligible community clusters, 306 women in the intervention group and 306 women in the enhanced usual care (EUC) group were enrolled between Jan 11, 2016, and Aug 21, 2016, and the results of 288 (94%) of 306 women in the intervention group and 290 (95%) of 306 women in the EUC group were included in the primary endpoint analysis. At 3 months, women in the intervention group had significantly lower mean total scores on the HADS than women in the control group (10·01 [SD 7·54] vs 14·75 [8·11]; adjusted mean difference [AMD] -4·53, 95% CI -7·13 to -1·92; p=0·0007). Individual HADS anxiety scores were also significantly lower in the intervention group than in the control group (5·43 [SD 4·18] vs 8·02 [4·69]; AMD -2·52, 95% CI -4·04 to -1·01), as were depression scores (4·59 [3·87] vs 6·73 [3·91]; AMD -2·04, -3·19 to -0·88). No adverse events were reported in either group. INTERPRETATION: Our group psychological intervention resulted in clinically significant reductions in anxiety and depressive symptoms at 3 months, and might be a feasible and effective option for women with psychological distress in rural post-conflict settings. FUNDING: WHO through a grant from the Office for Foreign Disaster Assistance.