One new phenolic glycoside (1) and two known stereoisomers (2 and 3) were isolated from the methanol extract of Viburnum cylindricum leaves. Their structures were determined as (7R,8S)-guaiacylglycerol 9-O-β-D-glucopyranoside (1), (7S,8R)-guaiacylglycerol 9-O-β-D-glucopyranoside (2), and (7R,8R)-guaiacylglycerol 9-O-β-D-glucopyranoside (3), respectively, by spectroscopic data (1D, 2D NMR, HR-ESI-MS, and ORD) and chemical methods. In addition, compound 1 showed potential α-glucosidase inhibitory activity with the IC50 value of 10.73 μM in comparison with the positive control acarbose (IC50 = 18.84 μM).