Abstract: To explore the relationship between friendship quality and maladaptive perfectionism among adolescents and its underlying mechanisms, this study administered the Friendship Quality Questionnaire, Growth Mindset Scale, Parental Psychological Control Scale, and Frost Multidimensional Perfectionism Scale to 519 middle school students in a city in Anhui Province. The results indicated that: (1) Friendship quality significantly and negatively predicted adolescents’ maladaptive perfectionism; (2) Growth mindset partially mediated the relationship between friendship quality and maladaptive perfectionism; (3) Parental psychological control moderated the latter part of the mediation model (i.e., "friendship quality → growth mindset → maladaptive perfectionism"). The protective effect of growth mindset was more pronounced under low psychological control but gradually weakened as psychological control increased. In conclusion, growth mindset partially mediated the association between friendship quality and maladaptive perfectionism, and parental psychological control moderated the second half of this mediation pathway.