Marasmus is a type of protein energy malnutrition and results from energy deficiency. Clinical features of marasmus are well-known, but its pathophysiology is still unclear. Since trace element deficiency and increased oxidative stress have been implicated in the pathogenesis of protein energy malnutrition, plasma selenium, copper, and zinc levels were studied in 36 marasmic and 24 well-nourished children. Plasma selenium, copper, and zinc levels of marasmic children were found significantly lower than those of control children (p < 0.001, p < 0.05, and p < 0.01, respectively). We concluded serum trace elements deficiency and increased oxidative stress may be contributing factors to the pathophysiology of marasmus and the replacement of these elements in the management of marasmus is important.