BackgroundThe under-five mortality rate is a reliable indicator of a country’s general level of development and the wellbeing of its children. Life expectancy is a good indicator of a population’s standard of living.ObjectivesTo identify Socio-demographic and Environmental determinants of under-five child mortality in Ethiopia.MethodsA national representative cross sectional study and a quantitative study were conducted among 5753 households selected based on 2019 Mini-Ethiopian Demographic and Health Survey (EDHS-2019) data. The analysis was done using STATA version 14 statistical software. Bivariate and multivariate analyses were used. To assess the determinants of under-five child mortality in multivariate analysis, p values less than 0.05 were considered statistically significant, and odds ratios with 95% CI (confidence interval) were used.ResultsA total of 5,753 children were included in the study. Sex of the head of the household being female (AOR = 2:350, 95% CI: 1.310, 4.215), the U5CM for being their mother were currently married (AOR = 2:094, 95% CI: 1.076, 4.072), The odds of U5CM was less by 80% (AOR = 1.797, 95% CI: 1.159–2.782) with the number of under-five children at the household born 2-4th order as compared to those children born on the first order. For the mothers visit anti natal care four and above visit (AOR = 1:803, 95% CI: 1.032, 3.149), for the way of delivery (AOR = 0:478, 95% CI: 0.233, 0.982).ConclusionMultivariate logistic analysis reflected that way of delivery, mothers had being currently marred, sex of the head of the household and number of antenatal care visit were found to be significant predictors of under-five child mortality. So, government policy, nongovernmental organizations, and all concerned bodies should be focused on the major determinants of under-five child mortality and put in a lot more effort to reduce under-five child mortality.