The present study aimed to evaluate the phytochemical constituents, total phenolic content, antioxidant activity, and hepatoprotective efficacy of Tabernaemontana divaricata bark extract against D-galactosamine-induced oxidative stress in rats. The bark of T. divaricata was extracted successively using petroleum ether, chloroform, methanol, and water. Phytochemical screening and estimation of total phenolic content were performed. The methanolic bark extract, which exhibited the highest phenolic content, was selected for in vivo evaluation. Hepatotoxicity was induced in Wistar rats using D-galactosamine (25 mg/kg), and the extract was administered orally at doses of 200 and 400 mg/kg for 21 days. Biochemical markers including SGOT, SGPT, ALP, ACP, bilirubin, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and lipid peroxidation levels were assessed. Phytochemical analysis revealed the presence of alkaloids, flavonoids, phenols, tannins, and triterpenoids. The methanolic extract showed the highest total phenolic content (207.09 ± 4.705 GAE mg/g) among all extracts. D-galactosamine administration significantly elevated hepatic biochemical markers and lipid peroxidation while reducing endogenous antioxidant enzymes. Treatment with T. divaricata methanolic bark extract produced a dose-dependent reduction in SGOT, SGPT, ALP, ACP, and bilirubin levels and significantly restored CAT, SOD, and GPx activities. The higher dose (400 mg/kg) demonstrated pronounced protection comparable to vitamin E treatment. The findings suggest that the plant may serve as a promising natural therapeutic agent for managing oxidative stress-associated hepatic disorders.