Obesity is caused from an imbalance between energy intake and expenditure, which may lead to pathologic growth of adipocytes and accumulation of fat in tissue. We examined the inhibitory effects of Eriobotrya japonica leaf and seed extracts on lipid absorption in vitro and fat accumulation during the differentiation of 3T3-L1 to adipocytes. 3T3-L1 preadipocytes were stimulated with DMEM media containing 10% FBS, 0.5 mM 3-isobuthyl-1-methyxanthine (IBMX), $5;{mu}g/ml$ insulin, and $1;{mu}g/ml$ dexamethasone for differentiation to adipocytes. E. japonica leaf extract at concentration of 0.5 or 1 mg/ml inhibited pancreatic lipase activity. The cell viability of 3T3-L1 adipocytes slightly reduced about 3% by treatment of E. Japonica leaf and seed extracts. The leaf and seed extracts of E. japonica effectively inhibited the accumulations of lipid droplet and expression of $C/EBP{alpha}$ promoting adipogenesis. Thus, this data suggest that E. japonica leaf and seed extracts inhibit fat accumulation through regulation of $C/EBP{alpha}$, and leaf extract is more effective in lipid absorption and adipogenesis than seed extract.