The aim of this study was to evaluate the effects of Nigella sativa (NS) supplementation in patients with ulcerative colitis. Two grams of NS powder or placebo were consumed for 6 weeks by 46 patients with active mild to moderate ulcerative colitis.Using valid and common questionnaires of colitis severity and blood sampling, we estimated disease activity index, quality of life, and some of inflammatory and oxidative stress factors at baseline and after 6 weeks of supplementation. NS-elevated tumor necrosis factor-alpha and high-sensitivity-c-reactive-protein as well as reduced malondialdehyde (p = 0.01, p = 0.02, and p = 0.005, respectively) compared with placebo. There was no significant difference between the two groups in serum total antioxidant capacity and nuclear factor kB levels. Total scores of Simple Clinical Colitis Activity Index Questionnaire and Inflammatory Bowel Disease Questionnaire-9were not different between the two groups; however, stool frequency score decreased significantly in NS group. Further clinical trials with different pattern of NS administration (the amount of total and divided daily doses, either powder type or standard extracts/oil and different time arrangement) are needed to clarify the vision.