Advanced glycation end products (AGEs) are known to be directly involved in diabetes mellitus and aging. Therefore, protective activities of isoimperatorin, imperatorin, byakangelicin, and oxypeucedanin hydrate from Angelica dahurica on the formation of AGEs were examined using an in vitro glycation reaction. Isoimperatorin showed strong inhibitory activity against the formation of AGEs. The inhibitory activity of isoimperatorin was more potent than that of the positive control, aminoguanidine. These results suggest that isoimperatorin from A. dahurica may be a promising agent for the treatment of glycation-associated diseases.