Sulfur mustard (SM) is a mutagenic compound that causes oxidative stress, antioxidant depletion even several years after exposure. Melatonin is an alternative medication that has antioxidant peroperties. The aim of this study was to investigate the effect of melatonin treatment on serum levels of several mineral elements, total antioxidant (TAC) and total oxidant status (TOS) in sulfur mustard-exposed patients. Victims with lung and sleep disorders was divided randomly to placebo and melatonin groups. They received melatonin or placebo for 56 days. Blood samples were taken before and after drug usage. The concentrations of serum trace elements (manganese, zinc, copper, and iron) and one other essential element (magnesium) were determined by graphite furnace and flame atomic absorption spectroscopy. TAC and TOS in serum were determined colorimetrically. Results showed that melatonin administration increases the magnesium and TAC concentrations. After the drug usage, placebo and melatonin groups had the highest TOS and TAC contents, respectively. Therefore, melatonin can be considered as a compound suitable for suppression of oxidative stress and helps to decrease oxidative damages induced by mustard gas.