Background: Undernutrition at the early stages of life can lower child resistance to infections, increase child morbidity and mortality and adequate nutrition is the keystone of survival, health and development hence Child under nutrition is a major public health problem in Ethiopia. Objectives: prevalence of the undernutrition and associated factors (wasting) among children 6 to 59 months of age in Debatie woreda Benishangul Gumuz Region. Methods: A community based cross-sectional study was conducted on 566 mother-child pairs of 6-59 month old children in February 2017. Anthropometric measurements of length/height and weight of 566 study children were taken and the socio-demographic characteristics of the subjects were collected using a questionnaire. Both anthropometric and non anthropometric data were entered using Epi-Info version 7. The data were analyzed using SPSS Version 20.0. Both Bivariate and multivariate analysis (logistic regression model) were used to identify the determinant factors associated with child under nutrition. Results: Result of the study revealed that the overall prevalence of under nutrition in the community 51.2 % , with 41.3% of the children being stunting, 12.5% children wasted and 27.2% for underweight. All three forms of under nutrition (stunting wasting, and underweight) were more prevalent among boys than girls with a statistically significant of P<0.05. ANC during pregnancy(AOR=2.4, 95%CI=1.27, 4.46), latrine (AOR=2.9,95%CI=1.53, 5.42), diarrhea episode for two weeks before the study period (AOR=3.7; 95%CI=2.03,6.76),material illiteracy (AOR=2.8,95%CI,=1.24,6.15), paternal illiteracy (AOR=2.9;95%CI= 1.59-5.43),income of (AOR=6.4; 95%CI=12.65,15.83) initiation of breast feeding,(AOR=2.9895%CI1.61-5.51) factors associated with wasting. maternal illiteracy (AOR=1.84,,95%CI,=1.14,2.96), the family income (AOR=2.07; 95%CI=1.24, 2.27),initiation of breast milk (AOR=1 1. .4 48 8 9 95 5% %C CI I 1 1. .0 0-2 2. .1 13 3) ) d du ur ra at ti io on n o of f b br re ea as st t f fe ee ed di in ng g, ,( (A AO OR R= =1 1. .6 62 2, ,9 95 5% %1 1. .0 0-2 2. .4 49 9) ) w we er re e v va ar ri ia ab bl le es s s si ig gn ni if fi ic ca an nt tl ly y a as ss so oc ci ia at te ed d w wi it th h s st tu un nt ti in ng g. . illiteracy of mother,(AOR=1.84,,95%CI,=1.14,2.96),family of lower income,(AOR=2.07; 95%CI=1.24, 2.27), initiation of breast feeding,(AOR=1.75 ,95%CI, 1.05, 2.49) ,frequency of feeding (AOR= 1.85,95%CI, (1.07,3.21) v va ar ri ia ab bl le es s s si ig gn ni if fi ic ca an nt tl ly y a as ss so oc ci ia at te ed d w wi it th h u un nd de er rw we ei ig gh ht t. . Conclusions: The prevalence of child undernutriton among the under five children was high, indicating that the nutrition situation in study area is very critical. Thus, undernutrition is a major public health problem. Further in-depth studies should also be encouraged to look for improved intervention.