This study intends to grasp the structural relation between adolescents‘ temperament (novelty seeking temperament, harm avoidance temperament), social support, emotion regulation, and then to investigate mediating effects of social support from the relationship between a adolescent’s temperament and emotion regulation. The study investigated 763 adolescents who are in the 2th grade of middle school. Results of the study are summarized as follows. Social support plays a complete medium role in temperament (novelty seeking temperament, harm avoidance temperament) and emotion regulation, which is deemed that temperament has indirect influence over emotion regulation through social support rather than having direct influence over emotion regulation. The results of this study will provide information for the improvement program for emotion regulation of adolescents.