We examined independent and interactive associations linking preadolescents' socially anxious feelings and peer victimization experiences with their social behaviors (rated by parents and teachers) and psychophysiological arousal during lab simulations of salient peer stress situations in preadolescence (peer evaluation and peer rebuff). Sixty-three preadolescents and one parent per preadolescent participated. Respiratory sinus arrhythmia (RSA), skin conductance level (SCL), and heart rate (HR) were assessed during peer stress situations. Preadolescents provided reports of social anxiety; preadolescents and parents reported on peer victimization; and parents and teachers rated prosocial and aggressive behaviors. Peer victimization moderated associations between social anxiety and both physiological arousal and social-behavior problems. As hypothesized, social anxiety was more strongly associated with lower RSA, higher HR, and higher aggressive behavior among preadolescents who experienced higher levels of peer victimization, compared to preadolescents who experienced lower levels of peer victimization.