Background: Markedly elevated aminotransferase levels are commonly encountered among hospitalized patients. However, data regarding the trajectory of enzyme elevation and disease-specific prognosis are limited. Methods: This study included 3237 patients with at least one episode of aspartate aminotransferase or alanine aminotransferase level being higher than 400 U/L between January 2010 and December 2019 at 2 centers. Patients were classified into 5 groups comprising 13 diseases according to etiology. Factors associated with 30-day mortality were evaluated using a logistic regression analysis. Results: The most common disease leading to markedly elevated aminotransferase level was ischemic hepatitis (33.7%), followed by pancreatobiliary disease (19.9%), DILI (12.0%), malignancy (10.8%), and viral hepatitis (7.0%). The 30-day all-cause mortality rate was 21.6%. The mortality rate for patients from the pancreatobiliary, hepatocellular, extrahepatic, malignancy, and ischemic hepatitis groups was 1.7%, 3.2%, 13.8%, 39.9%, and 44.2%, respectively. Age, etiology, and peak aminotransferase levels were independently associated with 30-day mortality. Conclusions: In patients with markedly elevated liver enzymes, the etiology and peak AST level are significantly associated with mortality.