The objectives of the present study were to adapt and analyze the factor structure, reliability, and validity of the Social Phobia and Anxiety Inventory for Children (SPAI-C; Beidel, Turner, & Morris, 1995) in a Spanish population. The SPAI-C was applied to a sample of 1588 children and adolescents with ages ranging from 10 to 17 years. The confirmatory factor analysis (CFA) showed a four-factor structure: Public performance, Assertiveness, Fear and avoidance/escape in social encounters, and Cognitive and psychophysiological interferences. Internal consistency was high (.90) and test-retest reliability was moderate (.56). Significant differences were found in the variables sex and age, although the effect size was small in both variables and their interaction. Overall, the increase of the age value was inversely proportional to that of social anxiety measured with the SPAI-C; in participants of the same age, values were higher for girls than for boys. Results suggest that the Social Phobia and Anxiety Inventory For Children is a valid and reliable instrument to assess social anxiety in Spanish children and adolescents.