Oxidative stress is considered to play an important role in the pathophysiology of hypertension. The aim of this research was to find out whether Clausena lansium (Lour.) Skeels of Wampee (WP) fruits extract attenuate the progression of high blood pressure, endothelial dysfunction and preservation of antioxidant status with using a nitric oxide synthase (NOS) inhibitor, N(G) (-nitro-L-arginine methyl ester (L-NAME) induced hypertension and oxidative stress in rats. Healthy adult male rats were received L-NAME at dose of 50mg/kg/day in drinking water for 4 weeks and were orally administered 250 or 500mg/kg of an aqueous extract of WP fruits extract daily for 2 consecutive weeks. Quercetin (QC; 25 mg/kg) was served as a positive control. The results showed that arterial blood pressure, vascular superoxide production, and plasma malondialdehyde level were markedly induced in L-NAME treated rats. In addition, serum nitric oxide, and glutathione levels were also reduced after L-NAME administration. However, daily administration with the high dose of WP fruits extract significantly alleviated these deleterious effects by attenuated high blood pressure, reversed the L-NAME-induced suppression in serum levels of nitric oxide, mitigated endothelial dysfunction, reduced oxidative stress and restored antioxidant glutathione. This suggests that WP fruits extract is a potential candidate for the development as a novel antihypertensive agents in the future.