The present study used a latent growth curve modeling approach to (a) examine the effectiveness of a brief self-compassion intervention on reducing impostor phenomenon, maladaptive perfectionism, and psychological distress and (b) explore who would benefit more from this intervention. A total of 227 college students at a large Midwest university were randomly assigned to participate in either a 4-week brief self-compassion intervention group or a nonintervention control group. Analyses of the effectiveness of the intervention suggested the brief self-compassion intervention had significant treatment effects for reducing impostor phenomenon and maladaptive perfectionism. Moreover, this study also examined whether participants with different levels of fear of self-compassion and core self-evaluation would report different levels of treatment effectiveness. Fear of self-compassion was found to be a significant moderator of the intervention effects in reducing maladaptive perfectionism and psychological distress. Specifically, participants in the intervention group with higher levels of fear of self-compassion reported a greater decline in both maladaptive perfectionism and psychological distress over time when compared to those with lower levels of fear of self-compassion. Core self-evaluation significantly moderated the effectiveness of this intervention in reducing participants' levels of impostor phenomenon and maladaptive perfectionism. Specifically, participants in the intervention group with lower core self-evaluation reported a greater reduction in maladaptive perfectionism over time when compared to those with higher core self-evaluation. Public Significance Statement By examining a brief online self-compassion intervention to reduce the levels of impostor phenomenon, this study contributes to improving college students' mental health. Our findings suggested that impostor phenomenon and maladaptive perfectionism have been reduced by the brief self-compassion intervention. This provides an important tool that could be used to tackle a salient mental health issue among the college student population.