The purpose of this study were to examine self-care behaviors and determine association between age, gender, last GPA, severity of illness, social support and self-care behaviors among school-age children with Thalassemia. Simple random sampling was used to recruit the sample of 91 school-age children who came to the Out Patient Unit of Thai Nguyen General hospital, Viet Nam to follow up their Thalassemia condition. Data were collected from February to March 2014. Research instrument consisted of a demographic questionnaire, the self-care behavior questionnaire, the perceived severity of illness’s scale and the social support questionnaire for children. Their internal consistency reliability were .97, .79, and .97, respectively. Data were analyzed by using descriptive statistics, Pearson correlation and independent t-test. Results revealed that total mean scores of self-care behaviors was 123.90 (S.D. = 22.51). There were positively significant correlations between child age, grade point average and social support and self-care behaviors (r = .65, p < .001, r = .75, p < .001, and r = .75, p < .001, respectively), and a negatively significant correlation between severity of illness and self-care behaviors (r = -.92, p < .001). In addition, it was also found that girls had better self-care behaviors than boys (t = 4.32, p < .001). These findings suggest that self-care behaviors of school-age children with Thalassemia have influences from many factors. Nurses and related health care providers for children should pay attention more on boys, increase social support for children and decrease children’s severity of illness through an intervention. Consequently, self-care behaviors of school-age children with Thalassemia would have appropriate self-care behaviors among school-age children with Thalassemia.