Metabolic syndrome (MetS) increases the risk of type 2 diabetes and cardiovascular diseases (CVD). Tea (Camellia sinensis), one of the most consumed beverages in the world, is rich in polyphenols, mainly catechins. Tea polyphenols may ameliorate obesity by reducing body weight, increasing energy expenditure and fat oxidation, stimulating lipolysis, and improving thermogenesis. Tea polyphenols also reduce the risks of type 2 diabetes (T2D), hypertension, hyperlipidemia, and inflammation. Results of clinical trials on the effects of the consumption of tea beverage, tea extracts, or isolated tea polyphenols on biomarkers of metabolic syndrome will be reviewed in this study. The effects of tea polyphenols on antioxidant status and low-grade chronic inflammation and the molecular mechanisms involved will also be discussed.