Abstract The multi-berries drink (MBD) has been demonstrated to possess high total polyphenol content and antioxidant activity measuring by ORAC and CAA assays. The influence of MBD supplement on endogenous antioxidant activity in healthy subjects was evaluated in this study. Twenty adults who smoke or drink alcohol regularly were allocated to MBD (100 mL/d, n = 10) or the control (placebo, 100 mL/d, n = 10) group for a 90-day, randomized, double-blind, placebo-controlled study. The results showed that MBD supplementation significantly increased glutathione (GSH), the activities of glutathione peroxidase (GSH-Px), glutathione reductase (GSH-Rd), superoxide dismutase (SOD) and decreased thiobarbituric acid reactive substances (TBARS) compared with the placebo. Additionally, hepatic and renal functions were not adversely altered in MBD-ingested subjects. It is suggested that MBD effectively promotes the endogenous antioxidant activity, and can be consumed as a functional supplement for people who are in danger of suffering oxidative-related chronic diseases.