INTRODUCTION: The study objective was to understand the effectiveness of Engaging Men through Accountable Practice (EMAP), a group-based discussion series which sought to transform gender relations in communities, on intimate partner violence (IPV), gender inequitable attitudes and related outcomes. METHODS: A two-armed, matched-pair, cluster randomised controlled trial was conducted between 2016 and 2018 in eastern Democratic Republic of Congo. Adult men (n=1387) and their female partners (n=1220) participated in the study. The primary outcomes of the study were female report of past year physical and/or sexual IPV and men's intention to commit violence. Secondary outcomes included men's gender attitudes, women's economic and emotional IPV, women's perception of negative male behaviours and perceived quality of the relationship. RESULTS: Men in EMAP reported significant reductions in intention to commit violence (β=-0.76; SE=0.23; p<0.01), decreased agreement with any reason that justifies wife beating (OR=0.59; SE=0.08; p<0.01) and increased agreement with the ability of a woman to refuse sex for all reasons (OR=1.47; SE=0.24; p<0.05), compared with men in the control group. We found no statistically significant differences in women's experiences of IPV between treatment and control group at follow-up (physical or sexual IPV: adjusted OR=0.95; SE=0.14; p=0.71). However, female partners of men in EMAP reported significant improvements to the quality of relationship (β=0.28; p<0.05) and significant reductions in negative male behaviour (β=-0.32; p<0.01). CONCLUSION: Interventions engaging men have the potential to change gender attitudes and behaviours in conflict-affected areas. However, while EMAP led to changes in gender attitudes and behaviours related to perpetration of IPV, the study showed no overall reduction of women's experience of IPV. Further research is needed to understand how working with men may lead to long-term and meaningful changes in IPV and related gender equitable attitudes and behaviours in conflict areas. TRIAL REGISTRATION NUMBER: NCT02765139.