Background: Children are most vulnerable to malnutrition in developing countries because of low dietary intakes, lack of appropriate care, and inequitable distribution of food within the household. Globally Malnutrition remains one of the most common causes of morbidity and mortality among under five children. In Ethiopia, child malnutrition rate is one of the most serious public health problem and the highest in the world. Objective: The main aim of this study was to assess under nutrition and associated factors Among Children Aged 6-59 months in Bahir Dar city Administration. Methods: A community based cross-sectional study design involving multistage sampling technique was implemented on 840 children aged 6-59 months from 16th of May to 25th of July 2016in Bahir Dar City Administration, Amhara region, Northwest Ethiopia. Data were entered and analyzed using EPI Info and SPSS respectively. Bivariate analysis and multivariable logistic regression model was used. Results: The prevalence of stunting, underweight and wasting was found to be 50.6%, 29.5% and 18.5% respectively. In the present finding showed that children whose families had fetched water for a distance of 15-30 minutes were 14.9 times more likely to be stunted than children whose families had fetched water at a distance less than 15 minutes [AOR =14.919; (95%CI: 2.930, 75.966)]. Regarding of wasting, children whose families had not functional toilet were 5.9 times more likely affected with wasting than whose families had functional toilet [AOR=5.951; 95%CI:(1.228, 28.841)]. Conclusion:The magnitude of under nutrition among under-five children was found to be very high in the study area. Under nutrition continued to be a substantial burden in the country.Special attention is needed for all concerned bodies since it was found to be serious and critical