This study was Quasi – experimental research. The purpose was the effect of health education program for application of self-efficacy theory on overweight student grade 4-6 primary school area 2 Khonkaen Primary Educational Service Area Office 1, Ban Ped sub - district, Mueang Khon Kaen district, Khon Kaen province. The samples were 47 overweight students in primary school area 2 consist of Kornprapaphat Bilingual School, Khamhai School, Bankok school and Bannongkham school. Data were collected by using the questionnaires. Data were analyzed by using percentage, mean, standard deviation and Paired sample t-test. The results of this study were as follow : 1. After receiving the health education program for application of self-efficacy theory, the samples had non-significantly perceived self-efficacy at .05 level. 2. After receiving the health education program for application of self-efficacy theory, the samples had significantly better knowledge about obesity, food consumption and exercise, outcome expectation and perceived food consumption and exercise behavior .05 level.