Nonalcoholic fatty liver disease (NAFLD) is a key component of metabolic syndrome ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH) and is now becoming the leading cause of cirrhosis and hepatocellular carcinoma worldwide. However, due to the complex and unclear pathophysiological mechanism, there are no specific approved agents for treating NASH. Breviscapine, a natural flavonoid prescription drug isolated from the traditional Chinese herb Erigeron breviscapus, exhibits a wide range of pharmacological properties, including effects on metabolism. However, the anti-NASH efficacy and mechanisms of breviscapine have not yet been characterized.We evaluated the effects of breviscapine on the development of hepatic steatosis, inflammation and fibrosis in vivo and in vitro under metabolic stress. Breviscapine treatment significantly reduced lipid accumulation, inflammatory cell infiltration, liver injury and fibrosis in mice fed a high-fat diet (HFD), a high-fat/high-cholesterol (HFHC) diet, or a methionine- and choline-deficient (MCD) diet. In addition, breviscapine attenuated lipid accumulation, inflammation and lipotoxicity in hepatocytes undergoing metabolic stress. RNA sequencing and multiomics analyses further indicated that the key mechanism linking the anti-NASH effects of breviscapine was inhibition of TAK1 phosphorylation and the subsequent MAPK signaling cascade. Treatment with the TAK1 inhibitor 5Z-7-oxozeaenol abrogated breviscapine-mediated hepatoprotection under metabolic stress. Molecular docking illustrated that breviscapine directly bound to TAK1.Breviscapine prevents metabolic stress-induced NASH progression through direct inhibition of TAK1 signaling. Breviscapine might be a novel therapeutic candidate for the treatment of NASH.This article is protected by copyright. All rights reserved.