Diarrhea is a major health problem in Ethiopia. Most importantly, burden of diarrhea is disproportionately high among under-five children. Therefore, the objective of this study was to assess the prevalence of diarrhea and its associated factors among under five children visiting Bahir Dar Health Center, Bahir Dar city, Northwest, Ethiopia, 2021. A hospital-based cross sectional study was conducted among under-five children from February to march 2021. Simple random sampling method was used to select the 200 participants. The socio-demographic data were collected by using structured and pretested questionnaire survey. Both univariate and multivariate logistic regression analyses were employed to identify predictor variables. Factors with a p-value of < 0.05 were considered as independently associated with diarrhea. Anthropometric measurements were used to collect height and weight following the standard measurement tools and procedures. Data was entered into SPSS version 23 and anthropometric measurements were converted into Z-score by WHO Anthro version 3.2.2 Software. The prevalence of diarrhea among under five children was 38% and intestinal protozoan parasite found to be 4% and intestinal helminthes 1%. In univariate analysis age group of child 7-12 were found to be (COR=2.429, CI: 0.849, 6.945), Maternal age group 18-24 (COR = 2.641 CI: 0.768, 9.074), wasting (COR= 2.769 CI: 0.748, 10.257) and hand washing only with water (COR = 4.667 CI: 0.374, 58.248) were predictors of the occurrence of diarrhea. In multivariate analysis ten of the risk factors found were not significantly associated with diarrhea infection (P<0.05). Complementary feeding at 6 month and putting complementary feeding in covered shelf were found to be protective against diarrhea. Keyword: Bahir Dar Ethiopia, Children, Diarrhea, Nutritional status Prevalence, Under-five