The Social Phobia and Anxiety Inventory – brief report (SPAI-B) is a questionnaire for adolescents developed from the Social Phobia and Anxiety Inventory (SPAI), one of the most studied and used instruments for the assessment of social anxiety in adults which additionally presents excellent psychometric properties. The present study analyzed the factor structure of the SPAI-B, its invariance across gender, as well as its psychometric properties in a sample of 593 Portuguese adolescents (333 girls and 260 boys), with an average age of 16. Results showed that the SPAI-B presented good fit indices for the one-factor model, once two pairs of errors were correlated. The invariance analysis of the factor model suggests that the construct of social anxiety has a similar expression in boys and girls. Furthermore, high values of internal consistency, test-retest reliability, convergent and divergent validity were also found. In conclusion, the SPAI-B presents good psychometric properties for the Portuguese adolescent population, in line with what has been found for the Spanish population.