This study aimed to investigate the antihypertensive effects of ethanolic extracts (EE) and compounds isolated from the small-leaf grape (Vitis thunbergii var. taiwaniana, VTT). The highest antiangiotensin-converting enzyme (anti-ACE) was found in stem-EE (IC50 was 69.5 μg/mL). In spontaneously hypertensive rats (SHRs), stem-EE effectively reduced blood pressure 24 h after administration of a single oral dose or when administered daily for 4 weeks. The isolated compounds, including (+)-vitisin A, ampelopsin C, and (+)-ε-viniferin, were shown to have anti-ACE and vasodilating effects against phenylephrine-induced tensions in an endothelium-intact aortic ring, with (+)-vitisin A being the most effective compound. Compared to control rats, SHRs showed significantly reduced systolic and diastolic blood pressures 24 h after a single oral dose of (+)-vitisin A (10 mg/kg) or captopril (2 mg/kg). These results suggest that the development of functional foods with VTT extracts may be beneficial for regulating blood pressure.