Background & Aims The Acute Kidney Injury Network (AKIN) criteria are widely used in nephrology, but information on cirrhosis is limited. We aimed at evaluating the AKIN criteria and their relationship with the cause of kidney impairment and survival. Methods We performed a prospective study of 375 consecutive patients hospitalized for complications of cirrhosis. One-hundred and seventy-seven (47%) patients fulfilled the criteria of Acute Kidney Injury (AKI) during hospitalization, the causes being hypovolemia, infections, hepatorenal syndrome (HRS), nephrotoxicity, and miscellaneous (62, 54, 32, 8, and 21 cases, respectively). Results At diagnosis, most patients had AKI stage 1 (77%). Both the occurrence of AKI and its stage were associated with 3-month survival. However, survival difference between stages 2 and 3 was not statistically significant. Moreover, if stage 1 patients were categorized into 2 groups according to the level of serum creatinine used in the classical definition of kidney impairment (1.5 mg/dl), the two groups had a significantly different outcome. Combining AKIN criteria and maximum serum creatinine, 3 risk groups were identified: (A) patients with AKI stage 1 with peak creatinine ⩽1.5 mg/dl; (B) patients with stage 1 with peak creatinine >1.5 mg/dl; and (C) patients with stages 2–3 (survival 84%, 68%, and 36%, respectively; p <0.001). Survival was independently related to the cause of kidney impairment, patients with HRS or infection-related having the worst prognosis. Conclusions A classification that combines the AKIN criteria and classical criteria of kidney failure in cirrhosis provides a better risk stratification than AKIN criteria alone. The cause of impairment in kidney function is key in assessing prognosis in cirrhosis.