Introduction: Melatonin’s potential goes beyond its chronobiotic role and owing to its non-toxic nature and high safety profile has also garnered much attention as a safe supplement to be used in humans. Aims and Objectives: The present study aimed to investigate time-dependent alterations in the sedentary population’s ability to fight oxidative stress brought on by long-term exogenous melatonin intake. Method: A single-blinded randomized controlled trial was carried out involving 28 healthy, sedentary young men aged between 21 and 26 years. Participants were randomly assigned to either the melatonin group (n=14) (MG) consisting of 14 individuals or the placebo group (n=14) (PG) also comprising 14 individuals. The MG received a daily oral dose of 3 mg of melatonin for four weeks, administered nocturnally 30 to 60 minutes prior to bedtime, while the PG received a placebo comprising of starch in gelatinous capsule. Measurements were taken weekly in the morning, with a six-day interval between consecutive sessions. Participants engaged in a treadmill running exercise according to a predetermined trial protocol, and blood samples were collected both before and after the exercise. Ethical clearance for the work was obtained from the Institutional Human Ethical Committee of the Department of Physiology, University of Calcutta. All the participants who took part in the study gave their written informed consent expressing their willingness. The study has been performed in accordance with the principles as suggested in the Declaration of Helsinki by the World Medical Association. Results: The serum levels of glutathione (GSH) and malondialdehyde (MDA), along with the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), were assessed. Additionally, markers of muscle damage were evaluated by measuring serum lactate dehydrogenase (LDH) and serum creatine kinase B (CK-B). A mixed model repeated measures analysis of variance (ANOVA) was conducted for independent samples to analyze the repeated measures of two factors: time and exercise, with a significance level established at p<0.05. The findings of the current study indicated a notable treatment effect regarding the concentrations of CAT and LDH in the melatonin group (MG) when compared to the placebo. The antioxidant defense system, as indicated by GSH and enzymes such as SOD and CAT, showed an increase in the MG, while their levels decreased following exercise. This suggests that melatonin has a beneficial role in mitigating exercise-induced oxidative stress. Additionally, a reduction in lipid peroxidation was observed, evidenced by lower levels of MDA in the MG, with the most significant effect occurring in Week 4. However, the results also indicate that melatonin did not significantly influence another muscle damage marker, CK-B isoform, in reducing exercise-induced oxidative stress among sedentary young men. Conclusion: Our current research supports the antioxidant capabilities of chronic nocturnal melatonin supplementation in reducing exercise-induced oxidative stress and muscle damage in sedentary young men.