Kombucha is a fermented beverage rich in bioactive compounds. This beverage has demonstrated high antioxidant capacity in vitro and experimental animal studies. In this sense, this study aimed to evaluate the effect of daily consumption of green tea kombucha on oxidative stress and endothelial health in individuals with excess body weight. This is a randomized controlled clinical trial, lasting 10 weeks, during which the control group followed a healthy -500 kcal/day energy-restricted diet. In contrast, the kombucha group, in addition to the energy-restricted diet, consumed 200 mL of kombucha green tea daily. This study included men and women aged 18 to 45 years without chronic diseases. At the beginning and end of the study, fasting blood was collected, and colorimetric assays and immunoassay protocols evaluated markers of oxidative stress and endothelial health. Compared to the control group, kombucha consumption significantly reduced hydrogen peroxide (H₂O₂) levels (p=0.007). Initial and final values were as follows: Control group (16.5 vs. 15.09 µmol/mL; n=29) and Kombucha group (18.14 vs. 14.67 µmol/mL; n=30). The other markers that were evaluated did not change after the kombucha consumption. In conclusion, daily consumption of 200 mL of green tea kombucha for 10 weeks reduces one pro-oxidant marker, without altering other markers of oxidative stress and endothelial health in individuals with excess body weight. Reducing a pro-oxidant marker suggests that kombucha is an antioxidant beverage with promising implications for human health. However, further studies are needed to elucidate other possible beneficial effects on health.