Social phobia/anxiety is a topic that has received considerable attention in adults and, to a lesser extent, in children and adolescents. One of the more widely debated issues in this area of research involves the assessment of social phobia/anxiety with self-report measures. Prior research papers (Caballo et al., 2010, 2012) have developed and validated a psychometrically sound instrument for assessing social anxiety in adults. This paper is the culmination of several years of research aimed at developing a new self-report measure for the assessment of social anxiety in children between the ages of 9 and 15, namely, the “Social Anxiety Questionnaire for Children” (SAQ-C24). The final version of this instrument for children consists of 24 items and almost fully replicates the factor structure of the prior questionnaire for adults, providing only one extra factor (six in total): 1) Speaking in public/Interactions with teachers, 2) Interactions with the opposite sex, 3) Criticism and embarrassment, 4) Assertive expression of annoyance or disgust, 5) Interactions with strangers, and 6) Performing in public. Furthermore, the questionnaire’s other psychometric properties are reported, and the results are compared for girls and boys. This research appears to confirm the structure of social phobia/anxiety centered on five/six dimensions.