Meeting the unique needs of high-achieving students is particularly challenging for professional counselors. Currently, there is a paucity of research that prioritizes the needs and social–emotional development of high-achieving students in accelerated curricula. This study examined the effectiveness of a modified version of the cognitive behavioral therapy for perfectionism (CBT-P) small group intervention on the perfectionism, negative affectivity, and social–emotional well-being of high-achieving students. A series of ANCOVA analyses revealed a statistically significant difference in negative affectivity and self-oriented perfectionism between treatment (n = 20) and comparison (n = 21) groups. No statistically significant difference was found regarding participants’ socially prescribed perfectionism or social–emotional well-being. The modified CBT-P yielded large effects (ηp2 = .22) in reducing negative affectivity and medium effects (ηp2 = .11) in reducing self-oriented perfectionism. These findings further support this population’s need for specialized school-based interventions and illuminate future research directions.