Acute kidney injury is defined as an abrupt decline in kidney function, which manifests as an increase in serum creatinine level or a decrease in urine output within a short period of time. It is a commonly encountered entity in the clinical setting and necessitates a systematic diagnostic approach. Acute kidney injury etiologies are classified as either prerenal, intrinsic renal, or postrenal. This article presents the key elements of history taking, physical examination, and laboratory investigations when assessing a patient for acute kidney injury to properly classify its etiology. The use of imaging modalities is also discussed. Common etiologies of acute kidney injury in each category are highlighted. Lastly, this article provides a brief overview of management principles for acute kidney injury with a particular emphasis on indications for initiation of dialysis.