Etiological models of nonsuicidal self-injury (NSSI) suggest interpersonal features may be important to understand this behavior, but social functions and correlates have not been extensively studied. This study addresses existing limitations by examining interpersonal correlates and functions of NSSI within a stratified random sample of 1,243 predominantly Caucasian college students (mean age = 21.52, SD = 4.15 years). Participants completed an anonymous online survey assessing NSSI features, perceived social support, and disclosure experiences. Approximately 15% of the students endorsed NSSI. Interpersonal reasons were endorsed proportionally more often for initiating rather than repeating the behavior. Individuals with repetitive NSSI reported significantly lower perceived social support from family members and fewer individuals to seek advice from than single-act and control participants. Fifty-nine percent had disclosed their NSSI, but rarely to mental health professionals. Conversations with others about NSSI were rated as being mostly unhelpful. These results emphasize the importance of interpersonal features and functions of NSSI, suggesting treatments should focus on strengthening interpersonal bonds alongside emotion regulation. Improving responses to disclosures of NSSI is needed to promote communication about this behavior and perceived helpfulness of such conversations.