In contrast to nonalcoholic fatty liver disease (NAFLD), metabolic-associated fatty liver disease (MAFLD) as an innovative definition can coexist with significant alcohol consumption. Massive clinical observations have indicated that high-fat/-calorie diet induced metabolic dysfunction along with alcohol intake deteriorates steatotic liver injury. To explore the potential mechanisms of fatty diet together with alcohol-induced steatohepatitis, we adopted a rat model by comparing a half-dose combination of fat diet (20%) and alcohol (10%) with their corresponding double dose of 40% fat diet and 20% alcohol for 8 weeks. The notable alterations in histopathology, acceleration in the oxidation parameters (ROS, NO and lipid peroxidation) and serum transaminase levels were shown in the concomitant group. Concomitant use of a high-fat diet and alcohol provoked hepatic endoplasmic reticulum stress, but did not activate mitochondria-mediated apoptosis parameters compared to F. In contrast, the notable activation of caspase-12 and nuclear translocation of CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) were observed only in the combined treatment group. The concomitant dietary fat intake and alcohol consumption lead to liver injury initially and later to steatohepatitis by the overdose of fat or alcohol, and in which the CHOP and caspase-12 might be involved in synergistic acceleration of steatohepatitis through a mitochondria-independent manner.