Background/Aims: ABO-incompatible (ABO-I) liver transplantation (LTx) may be mandatory in urgent conditions such as acute liver failure (ALF) or acute-on-chronic liver failure (ACLF) when deceased donor (DD) is unavailable or living donor (LD) selection is limited. This study specifically addresses the problem of urgent ABO-I LTx in critically ill adult patients having ALF or severely decompensated end-stage liver disease. Methodology: This series included 16 patients, 10 underwent ABO-I LD LTx and 6 underwent 7 ABO-I DD LTx. Multiple sessions of plasmapheresis reduced isoaglutinin titres to 1/16 or below, before and after LTx. Results: Mean follow-up period was 10.37 months (1 to 38). Median for MELD scores was 22.5 (17 to 30). Median survival was 9 months and mean survival was 19.5 months. Hospital mortality was 3 (18.7%). Two patients died due to small for size graft syndrome and cerebrovascular bleeding respectively. Hepatic artery thrombosis developed in 3 patients. Two of them died at postoperative 4th and 9th months. Third patient is still alive with hepatic necrosis problem. Conclusions: ABO-I LTx remains an important and unavoidable therapeutic option in adult patients with ALF or ACLF and urgent need for an allograft without the possibility to allocate a blood group compatible liver graft.