Regulation of diacylglycerol acyltransferase (DGAT) and pancreatic lipase (PL) activities is important in thetreatment of triacylglycerol (TG)-related metabolic diseases. Garcinia mangostana, also known as mangosteen, is a traditionalmedicine ingredient used in the treatment of inflammation in Southeast Asia. In this study, The ethanolic extract of G. mangostana peel inhibited human recombinant DGAT1 and DGAT2, and PL enzyme activities in vitro. The inhibitoryactivity of DGAT1 and DGAT2 enzymes of four representative bioactive substances in mangosteen was confirmed. Inaddition, G. mangostana was confirmed to suppress the serum TG levels in C57 mice by inhibiting the absorption andsynthesis of TG in the gastrointestinal tract. Through this study, it was revealed that G. mangostana extract could be useful forthe prevention and amelioration of TG-related metabolic diseases such as obesity and fatty liver.