Disability-inclusive development is important because there are a billion people with disabilities, and they often fall behind in income, education, health, and wellbeing. More and better evidence is needed on the effectiveness of how development interventions include and target people with disabilities. This review outlines some of the methodological challenges facing impact evaluations of disability-inclusive development interventions. Identifying people with disabilities is complex. Most approaches focus on impairment or functional limitations. They may or may not recognise environmental or personal factors, which influence the experience of disability. The Washington Group Short Set is widely endorsed for disability assessment; the addition of anxiety and depression items may enhance this tool further. The appropriate outcomes for the impact evaluation should be selected based on the aims and target audience of the intervention, the availability of appropriate tools, and after consultation with people with disabilities. New and better tools are needed to measure the range of impacts that may occur with greater accuracy, including impacts that are direct/indirect, proximal/distal, intended/unintended, and positive/negative. Disaggregation of data by impairment type is recommended to understand the effectiveness of interventions for different groups where the sample size is sufficient to allow meaningful comparisons. The inclusion of people with disabilities throughout the research process will improve the quality and acceptability of the study conducted.