A pharmacological inhibition of nitric oxide synthase (NOS) in rats produces renal vasoconstriction, renal dysfunction, and hypertension. The present study was aimed at investigating whether Bulbus Fritillaria water extract (BFWE) ameliorates NG-nitro-L-arginine methylester (L-NAME)-induced hypertension. Treatment of rats with L-NAME (60 mg/l drinking water, 4 weeks) caused a sustained increase in systolic blood pressure (SBP). The NO concentration in plasma and NO productions in the vascular tissues of the L-NAME-treated group were significantly reduced as compared with those in the control, whereas the expressions of NOS proteins were not altered. BFWE restored SBP to normal level in the L-NAME-treated hypertensive rats. Moreover, BFWE was able to preserve the vascular NO production and plasma NO metabolites concentration without changes of the expression NOS proteins. The renal functional parameters including urinary volume, sodium excretion, and creatinine clearance (Ccr) were significantly restored in rats co-treated with BFWE and L-NAME compared to the L-NAME-treated group. Taken together, these results suggest that BFWE prevents the increase of SBP in the L-NAME-induced hypertension that may have been caused by enhanced generation of vascular NO and amelioration of renal functions.