The present invention relates to a composition employing exosomes for prevention or treatment of acute liver failure. In an acute liver failure animal model, the present inventors experimentally identified that mice to which exosomes originating from adipose tissue-derived mesenchymal stem cells were injected survived at higher rates, had reduced levels of aspartate aminotransferase (AST) and alanine aminotransaminase (ALT), and were provided with excellent cell death inhibition and anti-inflammatory effects, compared with mice to which the exosomes were not injected. Thus, the composition of the present invention can be advantageously used for developing medical products and foods for preventing acute liver failure or alleviating or treating symptoms thereof.