The number of childhood cancer survivors is increasing as survival rates improve. However, complications after treatment have not received much attention, particularly metabolic syndrome. Metabolic syndrome comprises central obesity, dyslipidemia, hypertension, and insulin resistance, and cancer survivors have higher risks of cardiovascular events compared with the general population. The mechanism by which cancer treatment induces metabolic syndrome is unclear. However, its pathophysiology can be categorized based on the cancer treatment type administered. Brain surgery or radiotherapy may induce metabolic syndrome by damaging the hypothalamic-pituitary axis, which may induce pituitary hormone deficiencies. Local therapy administered to particular endocrine organs directly damages the organs and causes hormone deficiencies, which induce obesity and dyslipidemia leading to metabolic syndrome. Chemotherapeutic agents interfere with cell generation and growth, damage the vascular endothelial cells, and increase the cardiovascular risk. Moreover, chemotherapeutic agents induce oxidative stress, which also induces metabolic syndrome. Physical inactivity caused by cancer treatment or the cancer itself, dietary restrictions, and the frequent use of antibiotics may also be risk factors for metabolic syndrome. Since childhood cancer survivors with metabolic syndrome have higher risks of cardiovascular events at an earlier age, early interventions should be considered. The optimal timing of interventions and drug use has not been established, but lifestyle modifications and exercise interventions that begin during cancer treatment might be beneficial and tailored education and interventions that account for individual patients' circumstances are needed. This review evaluates the recent literature that describes metabolic syndrome in cancer survivors, with a focus on its pathophysiology.