Intensive Care Unit (ICU) is a specialized ward where critically ill patients are admitted to provide intensive health care Inappropriate antimicrobial therapy (AMT) and high mortality rates were documented in the ICU. The influence of irrational use of empiric antibiotics on clinical outcomes in ICU patients is not well studied in Sudan. This study aims to determine the rational use of antibiotics and its impact on clinical outcomes among ICU patients. Using data collection form, a retrospective longitudinal study was conducted among ICU patients at Omdurman Military Hospital, Khartoum State. Patients admitted from January 2019 to December 2019 were included in the study. Patients who stayed in ICU < 48 hr were excluded. Appropriateness of AMT is assessed using culture sensitivity test (CST) and the American Society of Infectious Diseases (IDSA) guideline. Among 102 patients, 54.9% male, one-third of patients developed nosocomial infections, 80.4% received empiric therapy with broad-spectrum antibiotics. The CST is done in 19%, and 43% patients are prescribed inappropriate AMT. Inappropriate AMT is associated with recurrent infections 38.4% (p=0.028) and high mortality 33.8% (p=0.014). Overall mortality rate 63.7% ICU patients. Elevated mortality in nosocomial 57.8%, decreased with inappropriate AMT in 21.6% patients. Significantly higher mortality rates 90.7% among uncontrolled infections (p<0.001), 80.6% nosocomial infections (p=0.001), and 76.7% renal compromised (p=0.002). Empirical AMT reduces the frequency of nosocomial infections, which has an impact on mortality. Inappropriate AMT is significantly associated with uncontrolled infections and lower mortality. Implementing a restrictive infectious control system and effective stewardship programs in hospital ICU wards is recommended.