ABSTRACT Background: Intensive care unit represent a multidisciplinary and inter-professional specialty dedicated to the total management of patients with acute life threatening condition. Now a day the care is advancing; however, in resource limited country like Ethiopia the care is very poor if any and mortality still high because of numerous reasons. Objective: To determine outcome with its associated factors of adult patient admitted to adult intensive care unit (AICU), Ambo University Referral Hospital, and Ambo. Ethiopia. Method: After obtaining ethical clearance, a retrospective institution-based cohort study was used. Data were retrieved from all intensive care unit (ICU) admitted patients (from September 2019 to December 2021) using a pre-tested structured questionnaire and the collected data was entered into Epi info and transported to SPSS for analysis. Risk factors and their associations were assessed by logistic regression, bivariate and multivariate logistic regression was used, P value 0.05 on multivariate logistic regression was considered statistically significant. Result: Five hundred and fifty patients have been admitted to the intensive care unit. However; only 390 patients had completed data and were analyzed. Majority 203 (52.1%) of participants were men and 155 patients were supplied by the medical service. The overall mortality rate was 46.9%, and significantly associated with Glasgow coma scale < 9 (AOR = 3.7, P value < 0.001), patient with coexisting disease (AOR = 2.2, P value 0.001). AOR = 1.9, P-value 0.011). mechanical ventilation requirements (AOR = 2.6, P-value 0.001) and patients who stayed less than four days in intensive care are more likely to die than patients who stayed longer than four days (AOR = 2.4, P value < 0.001). Conclusion and recommendation: The overall death rate in the intensive care unit is high and patient with low Glasgow coma scale, coexisting disease, need of mechanical ventilation short duration of stay are associated with mortality in intensive care unit. Therefore; we recommend the improvement of acute intensive care through the expansion of care, the provision of emergency equipment, drugs and human resources from different disciplines. Highlights