Acetaminophen (APAP) overdose-induced hepatotoxicity is the most commonly cause of drug-induced liver failure characterized by oxidative stress, mitochondrial dysfunction, and cell damage. Therapeutic efficacy of omega-3 polyunsaturated fatty acids (n-3 PUFA) in several models of liver disease is well documented. However, the impacts of n-3 PUFA on APAP hepatotoxicity are not adequately addressed. In this study, the fat-1 transgenic mice that synthesize endogenous n-3 PUFA and wild type (WT) littermates were injected intraperitoneally with APAP at the dose of 400 mg/kg to induce liver injury, and euthanized at 0 h, 2 h, 4 h and 6 h post APAP injection for sampling. APAP overdose caused severe liver injury in WT mice as indicated by serum parameters, histopathological changes and hepatocyte apoptosis, which were remarkably ameliorated in fat-1 mice. These protective effects of n-3 PUFA were associated with regulation of the prolonged JNK activation via inhibition of apoptosis signal-regulating kinase 1 (ASK1)/mitogen-activated protein kinase kinase 4 (MKK4) pathway. Additionally, the augment of endogenous n-3 PUFA reduced nuclear factor kappa B (NF-κB) – mediated inflammation response induced by APAP treatment in the liver. These findings indicate that n-3 PUFA has potent protective effects against APAP-induced acute liver injury, suggesting that n-3 dietary supplement with n-3 PUFA may be a potential therapeutic strategy for the treatment of hepatotoxicity induced by APAP overdose.