Garcinia mangostana L. (GM, family Guttiferae) is one of the most widely recognized tropical fruits. GM is a wealthy pool of xanthones that exhibit a wide range of bioactivities. Tovophyllin A (TA) separated from GM pericarps was tested for its efficacy to ameliorate acetaminophen (APAP)-induced liver injury. Mice were injected with a single dose of APAP with or without TA pretreatment. The protective effects of TA against APAP-induced liver damage were evident through amelioration of serum indices of hepatotoxicity and improvement of hepatic histopathologic lesions. TA has antioxidant activity because it inhibited APAP-induced lipid peroxidation and improved the antioxidant capacity of the liver. Also, TA enhanced the mRNA expression of nuclear erythroid-related factor 2 (Nrf2) and its target genes. Protein expression of Nrf2 and heme oxygenase-1 was enhanced remarkably in TA-pretreated groups. TA suppressed activation of nuclear factor-kappa B (NF-κB) and the subsequent release of pro-inflammatory cytokines. In conclusion, TA has a marked protective activity against APAP-induced hepatotoxicity which may be linked to its ability to activate Nrf2 and inhibit the NF-κB signaling pathway.