The present study compared the effects of classroom-based social skills training on the student's self-reported social skills and their subjective measures of adjustment (social support and loneliness). One hundred and eighteen 8th-grade students participated in this study. The training consisted of eight sessions during six months and focused on six target social skills: how to listen, how to invite classmates, how to give positive messages, how to reject unreasonable demands skillfully, how to control their emotions, and how to solve interpersonal problem. The training was implemented by classroom teachers using manuals and coached by specially trained facilitators. The training procedure in each session were comprised of instruction, modeling, rehearsal, feedback, reinforcement, and homework. Students made self-assessment on the social skills and on their subjective measures of adjustment (social support and loneliness) before and after the implementation of the entire training program. Based on changes from pre-assessment to post-assessment in terms of the self-reported social skills, the three groups (i.e., increased group, decreased group, and unchanged group) were identified. The increased group decreased in the withdrawn behavior score, whereas the decreased group increased in the aggressive behavior score and loneliness score. These results suggested that the classroom-based social skills training implemented in this study improved mostly students' social skills and their subjective adjustment for the increased group.