Soyasaponin Aa and soyasaponin Ab dose-dependently inhibited the accumulation of lipids and the expression of adiponectin, adipocyte determination and differentiation factor 1/sterol regulatory element binding protein 1c, adipocyte fatty acid-binding protein 2, fatty acid synthase, and resistin in 3T3-L1 adipocytes. In addition, Soyasaponin Aa and soyasaponin Ab suppressed the transcriptional activity of peroxisome proliferator-activated receptor γ (PPARγ) in HEK 293T cells. Furthermore, we confirmed that the expression of PPARγ and of CCAAT-enhancer-binding protein α± (C/EBPα±) was suppressed at both the mRNA and protein levels in 3T3-L1 adipocytes by treatment with Soyasaponin Aa and soyasaponin Ab.