In any country use of health services by elderly could vary according to the cultural, social, economic and demographic situation of the person who may need care. In certain contexts, it particularly varies with age and sex of the potential service user. However; there is paucity of information on the level and associated factors on health service utilization among elderly population in Ethiopia in general and in the study site in particular. To assess Factors Health Service Utilization and associated factors Among Older Adults in Ambo Town, West Shoa Zone, Oromia, Ethiopia. A community based cross sectional study carried out on 284 elderly populations residing in Ambo town from February- March 2018. The collected data was cleaned, coded and entered into computer and analyzed using SPSS windows version 20.0. Descriptive statistics were done to summarize data. Binary and multiple logistic regression was undertaken to determine the independent predictor of health service utilization.  The following factors were identified as determinants of health service utilization among the elderly in Ambo: a medical history of at least one chronic condition (OR = 1.737; [0.425-2.562]; p < 0.000), who had reported enough money to meet their need were 75% utilize health services when compared to participants who did not have enough money to meet their need 47.3% (OR = 1.587; 95% CI = [1.236 – 2.037], p = 0.004). Age, Income, education, medical history of at least one chronic condition and poor perceived health status were the most pervasive determinants of health service utilization. These factors could help health policy makers and health service providers identify and understand the situation of the elderly and consequently create conducive environment for providing appropriate health services.