Plant-derived natural products, recognized for their bioactive properties and minimal side effects, have been widely explored for their potential in obesity management. Identifying plant-based agents that can modulate adipocyte function with low cytotoxicity is essential for developing safe and effective anti-obesity interventions. In this study, Philadelphus schrenkii (Korean mock orange) was identified as a promising candidate following an initial screening for agents that exhibit minimal cytotoxicity and reduced adipocyte differentiation, as assessed by Oil Red O staining. The anti-obesity effects of P. schrenkii methanol extract (PSE) were evaluated by using in vitro and in vivo models. PSE treatment significantly reduced C3H10T1/2 preadipocyte differentiation and upregulated thermogenic markers, including Ucp1 and Dio2, in differentiated cells. Although PSE did not induce weight loss, alter food intake, or improve the serum metabolic profiles in a diet-induced obesity mouse model, it notably enhanced the thermogenic Ucp1 expression in inguinal white adipose tissue (iWAT) and brown adipose tissue. It also mitigated high-fat diet-induced adiposity in iWAT, accompanied by Protein Kinase A signaling activation. These findings suggest that PSE modulates adipose tissue function by suppressing adipogenesis and promoting thermogenic gene expression without weight reduction or metabolic improvement. Based on these effects, PSE may contribute as a supportive agent to plant-based therapeutic strategies against obesity