According to the Perfectionism Social Disconnection Model, interpersonal components of perfectionism (i.e., socially prescribed perfectionism, perfectionistic self-presentation) develop when individuals exhibit an inordinate need for belongingness and shame as a result of early attachment insecurity and/or a lack of emotional attunement in the caregiver–child relationship. This study hence examined the mediating effects of the need to belong and shame on the relationships between insecure attachment and interpersonal perfectionism. A sample of 513 undergraduates completed self-report measures including trait perfectionism, perfectionistic self-presentation, shame, the need for belongingness, and attachment styles. As hypothesized, socially prescribed perfectionism and perfectionistic self-presentation were both positively associated with the need to belong, shame, and insecure attachment styles. Furthermore, results from multiple mediation analyses indicated that the associations between preoccupied attachment and interpersonal components of perfectionism were mediated by a strong need for belongingness and shame. The present study hence provides further empirical support for the Perfectionism Social Disconnection Model and highlights the importance of examining the quality of attachment relationships for individuals with elevated interpersonal perfectionism.