BackgroundEvery year, polluted air is costing the globe 543,000 deaths of children under five. The particulate matter below 2.5 μm diameter (PM2.5) is a part of air pollution that has adverse effects on children’s health. In Ethiopia, the effect of ambient PM2.5is least explored. This study aimed to assess the association between PM2.5and under-five mortality in Ethiopia.MethodsThe study used the data from the Ethiopian Demographic Health Surveys conducted in 2016, collected between January 18 and June 27. All children under five who had data on child mortality and location coordinates were included in the study. Exposure to ambient PM2.5concentration was a satellite-based estimate by the Atmospheric Composition Analysis Group at Washington and Dalhousie University, in the United States and Canada, respectively. Annual mean pollution levels and mortality datasets were matched by children’s geographical location and dates of birth, death, and interview. The relationship between ambient PM2.5and under-five mortality was determined by a multilevel multivariable logistic regression on R software. The statistical analyses were two-sided at a 95% confidence interval.ResultsThe study addressed 10,452 children with the proportion of under-five mortality being 5.4% (95% CI 5.0–6.8%). The estimated lifetime annual mean exposure of ambient total PM2.5was 20.1 ± 3.3 μgm−3. A 10-unit increase in the lifetime annual mean ambient total PM2.5was associated with 2.29 [95% CI 1.44, 3.65] times more odds of under-five mortality after adjusting for other variables.ConclusionChildren under five are exposed to higher levels of ambient PM2.5concentration, exceeding the limit set by the World Health Organization. Ambient PM2.5is significantly associated with under-five mortality, adjusting for other variables. Strong measures need to be taken to reduce air pollution.