In the present study, effect of flavonoid glucopyranoside, isorhamnetin 3-О-β-D-glucopyranoside, from Salicornia herbacea on adipogenic differentiation were evaluated in 3T3-L1 adipocytes. Confluent 3T3-L1 preadipocytes in medium (0.5 mM methylisobutylxanthine, 0.25 µM dexamethasone, 5 µg/mL insulin, and 10% fetal bovine serum [FBS]) were differentiated into adipocytes for 6 days with/without isorhamnetin 3-О-β-D-glucopyranoside. The presence of isorhamnetin 3-О-β-D-glucopyranoside effectively suppressed adipogenic differentiation by downregulation of peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT/enhancer-binding proteins (C/EBPα), sterol regulatory element-binding protein 1 (SREBP1), and the adipocyte-specific proteins. Moreover, the specific mechanism mediating the effects of isorhamnetin 3-О-β-D-glucopyranoside was confirmed by activation of AMP-activated protein kinase (AMPK). These findings suggest that isorhamnetin 3-О-β-D-glucopyranoside exerts antiadipogenic activity through AMPK activation. This study should find the nutraceutical value of S. herbacea-derived glucopyranoside, isorhamnetin 3-О-β-D-glucopyranoside, as potent candidate of antiobesity agent via alleviation of lipid accumulation.