This study examines the utility of modifying the Social Anxiety Scale for Children—Revised (SASC-R) for use with adolescents and explores the associations between adolescents' social anxiety (SA) and their peer relations, friendships, and social functioning. The Social Anxiety Scale for Adolescents (SAS-A) was administered to 101 boys and 149 girls in grades 10 through 12. Factor analysis confirmed a three-factor structure: Fear of Negative Evaluation, Social Avoidance and Distress in General, and Social Avoidance Specific to New Situations or Unfamiliar Peers. Girls reported higher levels of SA than boys, and SA was more strongly linked to girls' social functioning, including fewer friendships, less intimacy, companionship, and support in close friendships. These findings extend the understanding of SA in adolescents, particularly highlighting its impact on girls' social functioning and close friendships. The study also evaluates gender differences in SA and the linkages between SA and interpersonal functioning, suggesting that socially anxious adolescents may face challenges in peer acceptance and romantic relationships.This study examines the utility of modifying the Social Anxiety Scale for Children—Revised (SASC-R) for use with adolescents and explores the associations between adolescents' social anxiety (SA) and their peer relations, friendships, and social functioning. The Social Anxiety Scale for Adolescents (SAS-A) was administered to 101 boys and 149 girls in grades 10 through 12. Factor analysis confirmed a three-factor structure: Fear of Negative Evaluation, Social Avoidance and Distress in General, and Social Avoidance Specific to New Situations or Unfamiliar Peers. Girls reported higher levels of SA than boys, and SA was more strongly linked to girls' social functioning, including fewer friendships, less intimacy, companionship, and support in close friendships. These findings extend the understanding of SA in adolescents, particularly highlighting its impact on girls' social functioning and close friendships. The study also evaluates gender differences in SA and the linkages between SA and interpersonal functioning, suggesting that socially anxious adolescents may face challenges in peer acceptance and romantic relationships.