Background: Pulmonary tuberculosis (TB) patients frequently present with compromised nutritional and antioxidant status, which may impair immune clearance of Mycobacterium tuberculosis. Vitamin C (ascorbic acid) has antioxidant and immune-supportive properties and has been proposed as a low-cost adjunct to standard anti-tuberculosis treatment (ATT). Objective: To evaluate the effect of vitamin C supplementation, given alongside standard ATT, on the rate of acid-fast bacilli (AFB) sputum smear conversion in newly diagnosed pulmonary TB patients during the intensive phase of treatment. Methods: A randomized, parallel-group study was conducted in 80 newly diagnosed, sputum-smear-positive, ATT-naïve pulmonary TB patients aged 20–65 years. Participants were allocated to receive either vitamin C (1000 mg/day) plus standard ATT (n=40) or placebo plus standard ATT (n=40). Sputum AFB smears were examined every two weeks for two months. Categorical outcomes were compared using the chi-square test; continuous outcomes (serum vitamin C levels) were compared using an independent-samples t-test. Significance was set at P