Background- Under nutrition is the most important risk factor for illness and death in worldwide. It is a public health problem of significant importance in developing countries and children are by far the most affected group. Objective- to determine the prevalence of under-nutrition of children among aged 24-59 months in terms of stunting and wasting and to identify its associated factors of Bahir Dar city of administration, Northwest Ethiopia. Methods- Community based cross sectional quantitative study was conducted from February to march, 2018. The study included 583 children from five kebeles were selected by simple random sampling technique. Interviewer administered structured questionnaires through interviewing mothers were used to collect data and Anthropometric measurement. The data entered using EPI INFO- 7 and analysis was done by SPSS-20. WHO Anthro software was used to calculate Weight-for height zscore and Height-for age z-score. Bivariate and Multivariate logistic regression analyses were used to identify factors associated with under-nutrition. A P-value <0.05 was considered to be statistically significant. Results- stunting & wasting were 37.9%, & 9.6%, respectively. Age 36-47months & 48-59months [AOR=3.26; (95% CI: 2.1,5.08)], [AOR=6.56;(95% CI: 3.99,10.76)] respectively, >5family size [AOR=1.597;(95% CI: 1.1, 2.33)] and being male [AOR=2.396;(95% CI: 1.62,3.53)] and duration of BF for <12 and between 12-24months [AOR=2.5;(95% CI:1.43, 4.396)], [AOR=1.78;(95% CI: 1.08, 2.92)] respectively, were significantly associated with stunting. Age 36-47 and 48-59months [AOR=2.83; (95% CI: 1.2, 6.6)], [AOR=9.29; (95% CI: 4.27, 20.24)] respectively, two weeks diarrhea [AOR=2.24; (95%CI: 1.204, 4.16)] and fever [AOR=3.77; (95% CI: 2.04, 7.03)] were predictors of wasting. Moreover, age of the children was a predictor of both stunting and wasting. Conclusion- This study shows that, the prevalence of stunting (37.9%) and wasting (9.6%) among children aged 24-59 months in Bahir Dar city administration was high. Being male, increasing age, large family size and breast feeding below 24months were factors associated with stunting. Increasing age, two weeks fever and diarrhea were factors associated with wasting.