This study firstly focused on development of an after-school program for school-aged children, and secondarily exploring the relationship between the after-school program and social competency of school-aged children. The program was composed of 10 two-hour sessions. The main goal of the program was to instill a sense of self-acknowledge, self-worth, responsibility and belonging to society and social activities. The subjects of this study were 29 children of first, second and third glades at the elementary schools in Seoul. This program was administered from March to May 1999. The data were analysed by frequency, mean, and paired t-test using the SAS program package. The major findings of this study were summarized as follows; There were significant differences in the degrees of social competency between before and after participating in the program(t=1,92 p<.05). The after-school program for school-aged children affect social competency variable as ‘initiative’(t=3,52 p<.001), but do not affect ‘sociability’, ‘responsibility’or ‘self-disclosure’. These results lead us to conclude that an after-school program of this type would be useful for developing peer-interation and for later social competency.