Social anxiety disorder is defined by an intense and distressing fear and avoidance of social situations with unfamiliar individuals, particularly those situations that provide the opportunity to be scrutinized (APA, 2013). A core feature of social anxiety involves fears of negative evaluation (FNE) and fears of positive evaluation (FPE). These core features are most commonly assessed using the Fear of Positive Evaluation Scale (FPES; Weeks et al., 2008) and the Brief Fear of Negative Evaluation Scale (BFNE; Leary, 1983). A robust line of evidence supports the psychometric properties of these measures when administered to adults; we know little about these measures’ properties when administered to adolescents. This study tests links between multi-informant reports on the FPES and BFNE and adolescents’ behavior within interactions with unfamiliar peers. We recruited 105 adolescents for the study. Adolescents completed a battery of measures examining their thoughts and behaviors and then completed social interaction tasks with a confederate. Parents completed a battery of questionnaires about themselves and their adolescent’s thoughts and behaviors. Both parents and adolescents provide reports about adolescents’ fears of evaluation that relate to adolescents’ observed behavior within interactions with unfamiliar peers. However, relative to parents’ reports, adolescents’ reports across FNE and FPE more robustly relate to observed behavior within these interactions. Further, across both informants and evaluative domains, FPE provide incrementally valuable information when understanding how adolescents behave within interactions with unfamiliar peers.