Diarrhea remains a major cause of mortality in children under 5 years of age in Sub- Saharan countries in Africa. The objective of this study was to assess the prevalence of diarrhea and associated factors among children under 5 years of age in ARFTH, Gofa and Signal health center of ministry of defense Addis Ababa,Ethiopia. A Health facility-based cross- sectional study was conducted among 348 children under 5 years of age but the sample size calculatedwas439, due to the limited duration from April 1toApril 30/2014 and non respondents, onlly348mothers were participated in thestudy.A questionnaire was used for collecting information on socio-economic characteristics, environmental hygiene and behavioral practices, and occurrence of diarrhea among children under 5 years of age.Result: the four-week prevalence of diarrhea among children under 5 years of age was 29.8%. Family income (OR =2.065, 95% CI: 1.205-3.533), Dipping water user (OR = 34.850, 95%CI: 17.996-67.489), Number of rooms (OR =2.805, 95% CI: 1.693-4.649), and Shared Latrine (OR=5.024, 95% CI; 2.997-8.422) were the major risk factors for diarrhea. This study demonstrated that diarrhea morbidity was relatively high among children under 5 years of age seen in Armed Forces Referral and Teaching Hospital, Signal health center and Gofa health center. Efforts to reduce childhood diarrhea should focus on improving household sanitation, ensure availability of private toilet facility and increasing number of rooms, construction of private toilet and avoid unsafe utilization of water. Methods; Proportional Quota sampling method based on number of patients and level of service used to obtain the study subjects from Armed Forces Referral land Teaching Hospital and Gofa,Signal health center.