The purpose of this study was to examine the ways in which implicit theories of intelligence, school goal structure, and social support influence achievement goal orientation in adolescents. The participants in this study were 493 second graders (270 boys and 223 girls) from three middle schools in Seoul. Data were collected by means of self-reported questionnaires and analyzed with descriptive statistics, Pearson's correlations, and hierarchical regression analysis. Adolescents were said to have a mastery goal orientation when they believed that their intelligence could be improved through the exertion of efforts. In addition, the more that adolescents perceived that their schools valued the process of understanding academic tasks, and as they received greater support from both parents and teachers, they tended to develop a mastery goal orientation. Adolescents were also said to have a performance goal orientation when they believed that their intelligence was fixed instead of malleable. In addition, as adolescents perceived that their schools valued students' grades and cared more for academically competent students, and as they received greater support from both parents and teachers, they were more likely to either possess or acquire a performance goal orientation. In conclusion, implicit theories of intelligence, school goal structure, and social support are variables which influence the development or acquisition of achievement goal orientation in adolescents. When adolescents perceive their environment as one in which their schools emphasize the understanding of learning tasks and they receive greater support from both parents and teachers, they tend to possess a mastery rather than performance goal orientation.