Objectives: This study aimed to evaluate the appropriateness of antibiotic use and factors associated with outcomes among sepsis patients in an intensive care unit (ICU). Methods: This cross-sectional study was carried out from February to May 2017 and included all adult patients with sepsis or septic shock admitted to the ICU of Dharmais Cancer Hospital, Jakarta, Indonesia. Data were collected from the patients' medical records. Results: A total of 60 patients with sepsis or septic shock were admitted to the ICU during the study period. The most common source of infection was hospital-acquired pneumonia (61.7%) and the majority had two or more comorbidities (93.3%). There were 115 antibiotic regimens prescribed. Overall, 33.3% of patients were prescribed inappropriate types of antibiotics and 51.7% were given an inappropriate dosage. The mortality rate was 68.3%. There was a statistically significant association between patient outcome and inappropriate doses of antibiotics (P = 0.034), although not inappropriate types of antibiotics (P = 0.050). A multivariate analysis indicated that the main factors influencing patient outcome were septic shock and the presence of at least two comorbidities (P <0.050 each). Conclusion: Inappropriate doses of antibiotics, a diagnosis of septic shock and the presence of at least two comorbidities were found to significantly increase the mortality rate of sepsis patients admitted to an ICU in Indonesia