Social fears arise when fearing to be judged in social events. When these fears are intense, persistent, and debilitating, the individual may suffer from social anxiety disorder (SAD), which has its most frequent onset during adolescence and tends to be chronic. Still, evidence on the prevalence of social fears and SAD in adolescence is scarce. This study analyzed the prevalence of social fears and of SAD in Portuguese adolescents. Of the initial sample (n = 1495), 26% presented with intense self-reported social fears. Of those, 53.9% accepted to be further assessed for diagnosis, resulting in a point-estimate prevalence of adolescent SAD of 9.4%; this is slightly higher than previously found. Social performance was the most feared social event. Of the adolescents with SAD, 12.9% were receiving psychological intervention, 12.1% refused intervention, and 92 (65.7%) accepted intervention. Findings confirm SAD as a highly prevalent mental disorder among adolescents, particularly girls, and additionally, that most of these adolescents did not seek treatment but are willing to receive help if made available. Hence, schools should be invested not only in identifying vulnerable adolescents but also in providing diverse intervention options, tailored to their needs, and directing them to successful developmental trajectories.