Angiotensin converting enzyme (ACE) plays a major role in the regulation of blood pressure. The potential antihypertensive activity of Angelica gigas was evaluated in vitro by its ability to inhibit ACE. A methanol extract of A. gigas roots exerted an inhibitory effect against ACE and was fractionated using several organic solvents, including dichloromethane, ethyl acetate, and n-butanol. The n-butanol soluble fraction, which manifested potent ACE inhibitory properties, was further purified via repeated silica gel and RP-18 column chromatography. Three benzopyriansides, such as nodakenin (1), umbelliferone (2), and umbelliferone 6-carboxylic acid (3) were isolated from A. gigas roots. Compounds 1-3 inhibited ACE activity in a dose-dependent manner, with $IC_{50}$ values of $63.95{pm}0.16$, $190.49{pm}0.54$, and $158.35{pm}1.53{mu}M$, respectively. The inhibition kinetics analyzed by Lineweaver-Burk plots revealed that the three compounds showed a mixed-type inhibition. The equilibrium constants for the inhibitor binding (Ki) of 1, 2, and 3 were estimated to be $1.56{ imes}10^{-4}$, $4.70{ imes}10^{-4}$, and $2.17{ imes}10^{-4}M$, respectively. We used A. gigas roots to isolate nodakinin, umbelliferone, and umbelliferone 6-carboxylic acid and tested their inhibition efficacy against ACE for the first time.