Obesity is a risk factor associated with numerous disorders, such as type 2 diabetes, hypertension, dyslipidemia and coronary heart disease. In this study, we investigated the inhibitory effects of Pericarpium zanthoxyli extract (PZE) on the adipocytic differentiation of OP9 cells. During adipocyte differentiation, the OP9 cells were treated with 0, 10 and 20 µg/ml of PZE at various time intervals, followed by the examination of lipid droplet formation and the mRNA expression of adipogenesis-related genes. The cells treated with PZE during the early period (days 0-2) showed a significant reduction in the accumulation of lipid droplets, which were induced by a standard adipogenic cocktail, as well as a decrease in the expression of the adipogenesis-related transcription factor, peroxisome proliferator-activated receptor γ (PPARγ) and PPARγ-target genes, such as adipocyte protein 2 (aP2), fatty acid synthase (FAS) and other adipocyte markers. Adipocyte differentiation was not inhibited by treatment with PZE during the late stage of differentiation (days 3-5). Thus, the inhibitory effects of PZE on adipocyte differentiation occurred during the early stages of adipogenesis, which was confirmed by the decrease in the levels of CCAAT/enhancer-binding protein β (C/EBPβ) in a dose-dependent manner when the OP9 cells were exposed to PZE. Taken together, our results indicate that PZE inhibit the early stages of adipogenic differentiation by inhibiting C/EBPβ expression.