In order to determine whether peach contains compounds to regulate adipocyte differentiation, extracts of flesh/pericarp of yellow/white peach were prepared in water, ethyl acetate (EtOAc), or n-butanol solvent and determined for effects on adipocyte differentiation in C3H10T1/2 or 3T3-L1 cells. Interestingly, none of peach extracts has statistically significant stimulatory effect on the adipocyte differentiation in C3H10T1/2. Furthermore, the presence of EtOAc extract of white peach pericarp (WPP) was found to inhibit lipid accumulation in 3T3-L1 cells both by microscopic examination of Oil Red O-stained lipid droplets and by spectrophotometric quantification of extracted stain, indicating a significant inhibitory effect on adipocyte differentiation. The inhibition of lipid accumulation was accompanied by a significant decrease in the expression levels of adipocyte molecular markers-peroxisome proliferator-activated receptor $gamma$, CAAT enhancer binding protein $alpha$, and fatty acid-binding protein. Thus, this study determined that WPP EtOAc extract contains the inhibitory compound(s) on adipogenesis.