Obesity, the global epidemic health problem, results in chronic disorders. Melatonin supplementation may prevent the adverse health consequences of obesity. The aim of this study was to assess the effects of melatonin supplementation on inflammatory and oxidative stress parameters in obese women. In randomized, double-blind, placebo-controlled trial, 44 obese women were randomly assigned to melatonin (n=22) and placebo (n=22) groups. Subjects were supplemented with a daily dose of 6 mg melatonin or placebo with low calorie diet for 40 days. Serum TNF-α, IL-6, hsCRP, TAC, and MDA levels were assessed before and after intervention. In the melatonin group, mean serum TNF-α, IL-6, hsCRP, and MDA levels decreased significantly (p<0.05) from 3.52±0.72 pg/ml, 27.12±6.32 pg/ml, 2.54±0.49 mg/l, and 3.81±0.29 nmol/l to 1.73±0.07, 16.34±6.32, 1.67±0.27, and 2.79±0.29, respectively. Whilst in the placebo group the decrease in values were not statistically significant. Mean TAC level increased slightly (from 1.11±0.30 to 1.14±0.45 mmol/l) in the melatonin group whereas it decreased slightly (from 1.13±0.15 to 1.08±0.21 nmol/l) in the placebo group. Significant differences were observed only for TNF-α (p=0.02) and IL-6 (p=0.03) between the 2 study groups. Considering the improvements in inflammatory and oxidative stress factors in obese women, it seems that melatonin supplementation may provide beneficial effects in obesity treatment by ameliorating some of its complications. However, further studies are needed to make concise conclusions.