Introduction: Acute kidney injury is a syndrome characterized by the rapid loss of the kidney's excretory function and is typically diagnosed by -the accumulation of end products of nitrogen metabolism (urea and creatinine) or decreased urine output, or both. In critically ill patients Acute Kidney Injury (AKI)occurs frequently and it allied with great rates of morbidity and mortality. Objective: This study aims to assess the prevalence, risk factors and outcome of acute kidney injury in patients admitted in the intensive care unit of Saint Paul's Hospital Millennium Medical College from January 2017 to December 2019. Methods: The study design was a facility-based retrospective; the cross-sectional study was conducted. Medical records of 108 were revised. Data collection checklist was developed and the data were extracted from the patients' medical records. Data entry and analysis were conduct by using the Epi-Data-4.2 and Statistical Package for the Social Sciences (SPSS) software version 25.0 respectively. The logistic regression model was used for analysis. Result: AKI in critically ill patients covered 16.1% with a mean age of 34 ± 15 age distribution and female predominance (66.7%). Being female and Anemia were the leading risk factors to develop AKI, 72 (66.7%)and 56 (51.9%) respectively. Sepsis was more likely associated to kill the patients with AKI. Most 81 (75%) AKI critically ill patients were initiated renal replacement therapy. Stage three AKI were account for 66(61.1%). Length of hospital stay ranged from 1 day to 52 days with a mean stay of 10.7 days. Critically ill patients with AKI (48.1%) had died in the study period. Conclusion: AKI is the most common cause for critically ill patient's morbidity I too observed the higher prevalence of AKI in critically ill patients with younger age groups and female predominance. The mortality rate of AKI in critically ill patients was near to half of all respondents during the study period.