INTRODUCTION: Improving complementary feeding in Ethiopia requires special focus on dietary diversity. The Sustainable Undernutrition Reduction in Ethiopia (SURE) programme is a government-led multisectoral intervention that aims to integrate the work of the health and agriculture sectors to deliver a complex multicomponent intervention to improve child feeding and reduce stunting. The Federal Ministries of Health and Agriculture and Natural Resources implement the intervention. The evaluation aims to assess a range of processes, outcomes and impacts. METHODS AND ANALYSIS: The SURE evaluation study is a theory-based, mixed methods study comprising impact and process evaluations. We hypothesise that the package of SURE interventions, including integrated health and agriculture behaviour change communication for nutrition, systems strengthening and multisectoral coordination, will result in detectable differences in minimum acceptable diet in children 6-23 months and stunting in children 24-47 months between intervention and comparison groups. Repeated cross-sectional household surveys will be conducted at baseline and endline to assess impact. The process will be assessed using observations, key informant interviews and focus group discussions to investigate the fidelity and dose of programme implementation, behavioural pathways of impact and contextual factors interacting with the intervention. Pathways of impact will also be explored through statistical analyses. ETHICS AND DISSEMINATION: The study has received ethics approval from the scientific and ethical review committees at the Ethiopian Public Health Institute and the London School of Hygiene and Tropical Medicine. The findings will be disseminated collaboratively with stakeholders at specified time points and through peer-reviewed publications and presentations.