Acute kidney injury (AKI) is associated with high mortality and morbidity risk. Factors predictive of mortality can guide in early identification of high-risk patients and escalation of therapy to improve outcomes. There is a paucity of data on AKI in Pakistan, and this study was done to determine in-hospital AKI mortality and the associated predictors of mortality. This was a prospective observational study conducted in the Acute Medical Unit and High Dependency Unit of Pak Emirates Military Hospital, Rawalpindi, from June to December 2018. Based on the Kidney Disease Improving Global Outcomes (KDIGO) AKI definition, 130 critically ill patients were included, while patients with chronic kidney disease were excluded. Data were collected on demographic profile-morbid conditions, etiology, laboratory values, and outcomes. The overall mortality was 45.4% (59/130) and varied with the stage of AKI, as it was 21.6%, 36.0%, and 61.8% in KDIGO stages 1, 2, and 3, respectively (P <0.05). There was a significant association (P <0.001) between sepsis, age >65 years, and mortality. Patients with inhospital mortality had higher median serum creatinine and mean potassium levels (P <0.01), with lower mean sodium levels and bicarbonate levels <10 mmol/L. However, on multivariate analysis using variables age >65 years, AKI stage 3, oliguria, bicarbonate <10 mmol/L, and sodium levels <130 mmol/L, only age [odds ratio (OR): 3.16, confidence interval (CI) 95%: 1.40-7.15), AKI stage 3 (OR: 3.12, CI 95%: 1.32-7.38], and low sodium levels <130 mmol/L (OR: 4.52, CI 95%: 1.40-14.61) were found to be independent predictors of mortality. Diabetes mellitus need for vasopressors, oliguria, hemodialysis requirement, and mean leukocyte counts had no significant association with mortality. AKI was associated with high in-hospital mortality in critically ill patients. Sepsis, hypertension, older age, Stage 3 AKI, higher mean creatinine, and potassium were predictive of increased mortality risk.