Multi-walled carbon nanotubes (MWCNTs) have been widely used in sewage disposal, water purification, and disinfection. Co-exposure to MWCNTs and heavy metal ions is common during water disposal. However, the hepatotoxicity of co-exposure to MWCNTs and lead ions for nonalcoholic fatty liver disease (NAFLD) subjects has not been investigated. NAFLD mice were fed intragastrically with MWCNTs and lead acetate (PbAc). Combined administration of MWCNTs and PbAc significantly damaged the liver function, and aggravated the nonalcoholic steatohepatitis phenotype as well as the hepatic fibrosis and steatosis in NAFLD mice. Furthermore, MWCNTs and PbAc significantly induced apoptosis in primary hepatocytes isolated from NAFLD mice. Combined administration of MWCNTs and PbAc also resulted in hepatic lipid peroxidation by inducing antioxidant defense system dysfunction, and significantly enhanced the expression levels of inflammatory cytokines in NAFLD mice livers. Meanwhile, combined administration of MWCNTs and PbAc may exert its hepatotoxicity in the NAFLD via inhibiting the adenosine 5‘-monophosphate activated protein kinase (AMPK)/peroxisome proliferator-activated receptors γ (PPARγ) pathway. Taken together, we conclude that co-exposure to MWCNTs and PbAc can remarkably aggravate the hepatotoxicity in NAFLD mice via inhibiting the AMPK/PPARγ pathway. This study may provide a biosafety evaluation for the application of nanomaterials in wastewater treatment.