The purpose of the study was to find out the effect of a comprehensive early intervention approach to intervene serious behavior problems. The subject was a 7-year-old boy who displayed difficult behaviors in his preschool classroom. A total of 30 sessions were administrated. The results showed that the subject' adaptive behaviors were improved, while the negative behaviors including aggressive and maladaptive behaviors, and critical negative events that occurs in the classroom setting were reduced. Additionally, the subject's activity engaged time and peer acceptance was increased. A discussion followed by the results was presented.