ObjectiveTo assess the effect of short birth interval (SBI) on neonatal, infant, and under-five mortality in Ethiopia.DesignA nationally representative cross-sectional survey.SettingThis study used data from the Ethiopia Demographic and Health Survey 2016.ParticipantsA total of 8448 women who had at least two live births during the 5 years preceding the survey were included in the analysis.Outcome measuresNeonatal mortality (death of the child within 28 days of birth), infant mortality (death between birth and 11 months) and under-five mortality (death between birth and 59 months) were the outcome variables.MethodsWeighted logistic regression analysis based on inverse probability of treatment weights was used to estimate exposure effects adjusted for potential confounders.ResultsThe adjusted ORs (AORs) of neonatal mortality were about 85% higher among women with SBI (AOR=1.85, 95% CI=1.19 to 2.89) than those without. The odds of infant mortality were twofold higher (AOR=2.16, 95% CI=1.49 to 3.11) among women with SBI. The odds of under-five child mortality were also about two times (AOR=2.26, 95% CI=1.60 to 3.17) higher among women with SBI.ConclusionSBI has a significant effect on neonatal, infant and under-five mortality in Ethiopia. Interventions targeting SBI are warranted to reduce neonatal, infant and under-five mortality.