Fatigue is a common symptom in children with cancer who are receiving chemotherapy or radiotherapy. Because the treatment of cancer in pediatric oncology patients involves intensive chemotherapy or radiotherapy treatment aimed at curing the condition, fatigue tends to be ignored by health care providers. This article aims to discuss "fatigue" from the following perspectives: definition, related conceptual/theoretical framework, studies related to pediatric oncology patients, assessment of fatigue, factors related to quality of life. The ultimate goal of this review is to provide guidelines for health care providers dealing with fatigue in pediatric oncology patients.