Two new phenolic compounds, (Z)-5'-hydroxyjasmone 5'-O-{6''-O-[(E)-caffeoyl]-b-d-glucopyranoside} (1) and quercetin-7-O-b-d-glucuronide methyl ester (2), along with ten known phenolic compounds, 3 – 12, were isolated from the aerial parts of Artemisia iwayomogi. Their structures were elucidated by spectroscopic methods, including 1D- and 2D-NMR, and HR-ESI-TOF-MS techniques. The inhibitory effects of compounds 1 – 12 on the LPS-stimulated production of IL-12 p40, IL-6, and TNF-a in bone marrow-derived dendritic cells were evaluated.