Antioxidant therapy has a potential to be introduced as therapeutic modality for chronic obstructive pulmonary disease (COPD) patients. This study aimed to determine the effect of antioxidant supplementation [ascorbic acid and N-Acetylcysteine (NAC)] on nutritional and antioxidant status in male COPD patients. A parallel and single blind randomised controlled clinical trial (RCT) was conducted at two medical centers in Kuala Lumpur, Malaysia. Seventy-nine subjects were recruited and randomly divided into four trial arms (i.e., NAC, vitamin C, NAC+vitamin C and control groups) for six mo. The primary outcome was changes in body mass index by estimating power of 90% and significance level of p<0.05. Repeated Measure ANOVA showed that there was a significant interaction effect on BMI (p=0.046) and carbohydrate intake (p=0.030), especially in the NAC group. Plasma glutathione (GSH) increased significantly in all intervention groups, especially in vitamin C (p=0.005). A single supplementation of NAC or vitamin C improved nutritional and antioxidant status of subjects.