Yerba Mate, derived from the leaves of the tree, Ilex paraguariensis, is widely-used as a tea or as an ingredient in formulated foods. The aim of the present study was to evaluate the effects of Yerba Mate extract on weight loss, obesity-related biochemical parameters, and diabetes in high-fat diet-fed mice.To this end, by using in vivo animal models of dietary-induced obesity, we have made the interesting observations that Yerba Mate has the ability to decrease the differentiation of pre-adipocytes and to reduce the accumulation of lipids in adipocytes, both of which contribute to a lower growth rate of adipose tissue, lower body weight gain, and obesity. Our data from in vivo studies revealed that Yerba Mate treatment affects food intake, resulting in higher energy expenditure, likely as a result of higher basal metabolism in Yerba Mate-treated mice. Furthermore, in vivo effects of Yerba Mate on lipid metabolism included reductions in serum cholesterol, serum triglycerides, and glucose concentrations in mice that were fed a high fat diet. In conclusion, Yerba Mate can potentially be used to treat obesity and diabetes.