Sepsis is a serious medical problem and is one of the main causes of high mortality in intensive care units. Fifty percent of patients with severe sepsis will develop acute lung injury (ALI). Amentoflavone (AMF) is a polyphenolic compound possessing potent anti-inflammatory activities. The study aimed to explore the protective effects of AMF against ALI in cecal ligation and puncture (CLP)-induced septic rats. The results showed that AMF administration protected against septic ALI, as reflected by marked amelioration of histological injury of lung tissues and decrease of pulmonary edema in CLP-treated rats. AMF ameliorated CLP-induced increase of systemic and lung TNFα and IL-1β and binding activity of p65 NF-κB, indicating the inhibition of inflammation. Moreover, AMF prevented CLP-induced oxidative stress, as evidenced by increase of oxygen consumption rate, decrease of TBARS content, increase of SOD activity and GSH level in lung tissue of CLP-treated rats. CLP resulted in significant decrease of mRNA expression of Nrf2 and GCLc, which was inhibited by AMF. AMF-induced protective effects on ALI, inflammation, and oxidative stress were inhibited by lentivirus shRNA-mediated silence of Nrf2 and buthionine sulphoximine (BSO), an inhibitor of GSH synthesis. AMF increased Nrf2-binding activity in GCLc promoters in lung tissue of CLP-treated rats. The results suggested that AMF protected against ALI in septic rats through upregulation of Nrf2-GCLc signaling, enhancement of GSH antioxidant defense, reduction of oxidative stress and final amelioration of inflammation and histological injury of lung. The data provide new therapeutic options for the treatment of sepsis-associated ALI.