The aim of this study was to examine the antioxidant activity of ginger extract oral supplement in newly diagnosed cancer patients receiving adjuvant chemotherapy compared to placebo. Newly diagnosed cancer patients receiving moderate-to-high emetogenic potential adjuvant chemotherapy were randomized to receive either a ginger extract (standardized 6-gingerol 20 mg/day) or a placebo 3 days prior to chemotherapy, which they continued daily. Oxidant/antioxidant parameters, including the activities of superoxide dismutase (SOD) and catalase (CAT) and levels of glutathione peroxidase (GPx), total glutathione (GSH/GSSG), lipid peroxidation products detected as malondialdehyde (MDA) and NO /NO , were measured at baseline and at days 1, 22, 43 and 64 after undergoing chemotherapy. Two-sided statistical analysis, with < 0.05, was used to determine statistical significance. A total of 43 patients were included in the study: 19 and 24 patients were randomly assigned to the ginger group and placebo group, respectively. Antioxidant activity parameters, including SOD, CAT, GPx and GSH/GSSG, were significantly increased at day 64 in the ginger group compared to those in the placebo group, while MDA and NO /NO levels were significantly decreased ( < 0.0001). When compared to the baseline, the activities of SOD and CAT and the levels of GPx and GSH/GSSG were significantly higher on day 64 ( = 0.01), while the blood levels of MDA and NO /NO were significantly decreased ( < 0.01). Daily supplement of ginger extract started 3 days prior to chemotherapy has been shown to significantly elevate antioxidant activity and reduce oxidative marker levels in patients who received moderate-to-high emetogenic potential chemotherapy compared to placebo.