This study examined adolescents' interpersonal functioning, including the qualities of their closest friendships and romantic relationships, as predictors of dating/heterosocial anxiety. An ethnically diverse sample of 781 adolescents (57% girls; ages 15-19 years) completed measures that assessed the number and type of close friends, the presence of a romantic relationship, the qualities of their best same-sex friendship and their romantic relationship (using the Network of Relationships Inventory-Revised), and levels of dating or heterosocial anxiety (using the Dating Anxiety Scale for Adolescents). Most adolescents were romantically involved, and girls were more likely to have a romantic partner than boys. Adolescents with fewer other-sex friends and those with less positive and more negative interactions with their best friends reported high levels of dating anxiety. In addition, adolescents who reported never having a romantic relationship, who did not have a current romantic partner, and who had less positive and more negative interactions with their romantic partners reported higher levels of dating anxiety. Variations were noted for different aspects of dating anxiety. The findings indicate that multiple aspects of adolescents' social relations may be independently and uniquely related to feelings of distress in dating or heterosocial situations. Adolescents' social relationships have the potential to support or interfere with the development of successful romantic relationships.