This research investigated associations between socially prescribed and self-orientated perfectionism, and the social functioning of 510 preteens (M = 11.2). The study focused on predictions from the Perfectionism Social Disconnection Model (PSDM) by determining whether rejection sensitivity and social isolation, in that sequence, mediated the associations between both perfectionism types and mental health outcomes. Employing both survey and experimental methods, findings indicated that both types of perfectionism in preadolescence were associated with increased interpersonal difficulty, rejection sensitivity and feelings of social isolation, as well as higher levels of eating disorder symptoms, depression, and anxiety. Results from serial mediation analyses found general support for the theoretical predictions of the PSDM for socially prescribed perfectionism, and extending upon previous research, for self-orientated perfectionism. The age of the sample suggests that both forms of perfectionism may be important targets in programs to prevent the development of mental health problems.