Domoic acid (DA) is a neuroexcitatory amino acid that is produced by Pseudo-nitzschia during harmful algal blooms (HAB). Accumulation of DA can be transferred through food chain and cause neuronal damage in marine animal and in human. Like other algal toxins, DA was suggested to increase the oxidative stress and increase the detoxification-related gene expression in fish. The widely used food antioxidant, tert-butylhydroquinone (tBHQ), was known to induce a wide range of antioxidative potentials such as elevation of the glutathione levels and glutathione S-transferases (GSTs), via the activation of antioxidant response elements (AREs). In this study, the influences of dietary tBHQ on domoic acid (DA) metabolism and detoxification-related gene transcription were investigated both in vivo and in vitro. Oral administration of tBHQ resulted in significant decreases of DA accumulation of liver tissues in which red sea bream were fed with a single dose of 10 mg DA and 100 mg tBHQ per kg body weight per fish. Real-time PCR further revealed that the mRNA levels of AHR/ARNT/CYP1A1/GSTA1/GSTR were up-regulated in the above liver tissues at 72 h post tBHQ treatment. In consistence, tBHQ exposure also resulted in increased mRNA transcription of GSTA1, GSTA2 and GSTR in cultured red sea bream hepatocytes. Collectively, our findings in this research suggested that the dietary intake of tBHQ accelerated DA metabolism in fish, through mechanisms involving altered transcription of detoxificationrelated liver genes. Domoic acid is an excitatory neurotoxin produced by marine diatoms of the genus Pseudo-nitzschia. It is responsible for a neurotoxic disease called amnesic shellfish poisoning (ASP) in human and marine mammals following consumption of DA (domoic acid)-contaminated fish. Symptoms of ASP include short-term memory loss, brain damage and death in severe cases. During harmful algal blooms, accumulation of high concentration of DA has been reported for a number of marine species such as types of cockles (Cerastoderma edule), crabs (Cancer magister), furrow shell (Scrobicularia plana), mussels (Mytilus edulis), razor clams (Siliqua patula) and scallops (Pecten maximus) [1][2][3]. Other fish species, such as anchovies and mackerel, have also been shown to accumulate DA, although at much lower levels compared with those found in shellfish [3]. A majority of DA uptake was excreted via kidney and bile in fish, with the remaining absorbed DA mainly detected in liver, heart, spleen and muscle [4]. Limited data was available on in vivo metabolism in fish, although previous studies suggested that the biotransformation and detoxification pathways of Phase I and/or Phase II xenobiotic metabolism enzymes (XMEs) were involved in DA metabolism [5]. Further investigations using intraperitoneal (I.P.) injection of DA in fish revealed that a receptor-mediated induction of