Citrus unshiu has recently been studied in several studies for various biological effects, including anti-inflammatory effect, anti-osteoporosis, and antibacterial effect. However, its anti-obesity effect has not been studied. In this study, the anti-obesity effect was analyzed through cell experiments using Oil Red O staining and western blot. In addition, the anti-obesity effect was analyzed through animal experiments using blood chemistry analysis, H&E staining, immunohistochemistry, RT-PCR, and ELISA. The 30% ethanol extract of Citrus unshiu peel most effectively inhibited adipocyte differentiation through the PPARγ-C/EBPα pasway. Animal studies have shown anti-inflammatory effects, including LDL and leptin levels, inhibiting fat accumulation, preventing lipogenesis through regulation of PPARγ-C/EBRα-FAS, and down-regulating IL-1β, IL-13, and TNF-α. The active ingredients of Citrus unshiu are believed to be narirutin and hesperidin, suggesting that it is an anti-obesity and anti-inflammatory agent by regulating leptin levels.