The present study investigates the possible ameliorative effects of diallyl trisulfide (DATS) against arsenic (As)-induced hepatotoxicity and oxidative stress in rats. The four experimental groups evaluated include: (1) vehicle control; (2) As (5 mg/kg/day); (3) DATS (80 mg/kg/day) + As; and (4) DATS. Induction of As in rats caused severe hepatotoxicity as evidenced by an elevation of serum aspartate aminotransferase and alanine aminotransferase activities and increased total bilirubin concentration, indicating hepatic function abnormalities. Histopathological examination revealed various structural changes in the liver, characterized by hepatocyte degeneration/necrosis, congestion, sinusoidal dilatation, vacuolation, and inflammatory cell infiltration. The significant decrease in reduced glutathione content, catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase activities and the significant increase in lipid peroxidation (thiobarbituric acid reactive substance) and protein oxidation (protein carbonyl) contents indicated that As-induced hepatotoxicity was mediated through oxidative stress. As intoxication also elevated the levels of Cas-3 and nitric oxide and increased the expression of nuclear factor-κB p65 in the liver. In contrast, DATS pretreatment significantly improved As-induced serum biochemical, immunohistochemical, and histopathological alterations reflecting hepatic dysfunction. These results may contribute to a better understanding of the hepatoprotective role of DATS, emphasizing the influence of this garlic trisulfide in the diet for human health, possibly preventing the hepatic injury associated with As intoxication, presumably due to its ability to inhibit lipid peroxidation, protein oxidation, and restoration of antioxidant status.