The purpose of this study was to identify difficulties in addressing problem behavior of school-age children and to help them and their family members understand family functions, communication methods, and draw new solutions through family play therapy programs. The results of this study are as follows: First, the program has 13 sessions in total, and each session have 3 sections: relaxation play, therapy activities, and feedback sharing, and conducted once a week, for 60 minutes. Second, the family play therapy program developed in this study helped improve the problem behavior of school-age children by participating not only in school-age children, but also in the whole family including parents and siblings. Third, This program improved marital intimacy through marital emotional support stage activities for participating parents, and brought about positive changes in the perception of the role of parents and family function. This study is especially meaningful in that at a time in which there are few studies using similar methods, a practical program enabling a whole family to participate in helping their school-age children with problem behavior was developed and effectively applied.