ABSTRACT: BACKGROUND:Sugira Muryango is a father-engaged early child development and violence-prevention home-visiting programme delivered by trained lay workers. This cluster-randomised trial evaluates whether families living in extreme poverty (Ubudehe 1, the poorest category in the Government of Rwanda's wealth ranking) who receive Sugira Muryango in combination with a government-provided social protection programme demonstrate greater responsive, positive caregiving, nutrition, care seeking, hygiene, and father involvement compared with control families receiving usual care (UC). METHODS:Using detailed maps, we grouped closely spaced villages into 284 geographic clusters stratified by the type of social protection programmes operating in the village clusters; 198 clusters met all enrolment criteria. Sugira Muryango was delivered to n =?541 families in 100 treatment clusters with children aged 6-36?months living in extreme poverty. We assessed changes in outcomes in intervention and n =?508 UC control families using structured surveys and observation. Analyses were intent to treat using mixed models to accommodate clustering. RESULTS:Families receiving Sugira Muryango improved on core outcomes of parent-child relationships assessed using the Home Observation for Measurement of the Environment (Cohen's d =?0.87, 95% CI: 0.74, 0.99) and the Observation of Mother-Child Interaction (Cohen's d =?0.29, 95% CI: 0.17, 0.41). We also saw reductions in harsh discipline on items from the UNICEF MICS (OR?=?0.30: 95% CI: 0.19, 0.47) and in violent victimisation of female caregivers by their partners (OR?=?0.49, 95% CI: 0.24, 1.00) compared with UC. Moreover, children in families receiving SM had a 0.45 higher increase in food groups consumed in the past 24?h (Cohen's d =?0.35, 95% CI: 0.22, 0.47), increased care seeking for diarrhoea (OR?=?4.43, 95% CI: 1.95, 10.10) and fever (OR?=?3.28, 95% CI: 1.82, 5.89), and improved hygiene behaviours such as proper treatment of water (OR?=?3.39, 95% CI: 2.16, 5.30) compared with UC. Finally, Sugira Muryango was associated with decreased caregiver depression and anxiety (OR?=?0.58, 95% CI: 0.38, 0.88). CONCLUSIONS:Sugira Muryango led to improvements in caregiver behaviours linked to child development and health as well as reductions in violence. TRIAL REGISTRATION:ClinicalTrials.gov number NCT02510313.