A correlational descriptive study was conducted to investigate self-concept and selected influencing factors among hospitalized Chinese school-age children with a chronic illness. The purposive sample was composed of 122 school-age children with chronic illnesses, such as nephrotic syndrome, leukemia, and congenital heart disease, who were admitted to three major teaching hospitals in Shanghai City. The children's medical records, demographic forms, and the Piers-Harris Self-concept Scale (PHSCS) were used to collect the data. Descriptive statistics, and stepwise multiple regression were used to analyze the data utilizing the SPSS program (SPSS Inc, Chicago, IL, USA). The results of this study showed that the majority of hospitalized Chinese school-age children with a chronic illness had at least an average level of self-concept. Academic achievement (grade point average) was a strong predictor of self-concept, as are most of its subconcepts, including social behavior, academic competence, and physical appearance and attributes. Age was a significant predictor of overall self-concept, social behavior, and popularity subconcept. Sex was a significant predictor of self-concept subconcepts such as social behavior, anxiety, and popularity. Duration of illness was a significant predictor of physical appearance and attributes. In addition, the type of illness was a significant predictor of popularity. It can be concluded that the importance of school education should be emphasized by hospital and school nurses for the purpose of helping such children build a positive self-concept concerning their age, sex, academic achievement, type of illness, and duration of illness. Recommendations for further research have been suggested.