Background: Community health worker (CHW) programmes are a valuable component of primary care in resource-poor settings. The evidence supporting their effectiveness generally shows improvements in disease-specific outcomes relative to the absence of a CHW programme. In this study, we evaluated expanding an existing HIV and tuberculosis (TB) disease-specific CHW programme into a polyvalent, household-based model that subsequently included non-communicable diseases (NCDs), malnutrition and TB screening, as well as family planning and antenatal care (ANC). Methods: We conducted a stepped-wedge cluster randomised controlled trial in Neno District, Malawi. Six clusters of approximately 20 000 residents were formed from the catchment areas of 11 healthcare facilities. The intervention roll-out was staggered every 3 months over 18 months, with CHWs receiving a 5-day foundational training for their new tasks and assigned 20–40 households for monthly (or more frequent) visits. Findings: The intervention resulted in a decrease of approximately 20% in the rate of patients defaulting from chronic NCD care each month (−0.8 percentage points (pp) (95% credible interval: −2.5 to 0.5)) while maintaining the already low default rates for HIV patients (0.0 pp, 95% CI: −0.6 to 0.5). First trimester ANC attendance increased by approximately 30% (6.5pp (−0.3, 15.8)) and paediatric malnutrition case finding declined by 10% (−0.6 per 1000 (95% CI −2.5 to 0.8)). There were no changes in TB programme outcomes, potentially due to data challenges.