Despite the increased use of social and emotional learning (SEL) programs, empirical research is hindered by lengthy assessment options, difficult to fit into educational contexts. To cover these needs, the Social Skills Improvement System SEL Brief Scales -- Student Form (SSIS SELb-S) was developed. Although it has been translated into several languages, a Portuguese version with sound psychometric properties is still missing. This study aimed to develop the Portuguese version (SSIS SELb-Spt) and to examine its psychometric properties. METHODS: After translating the original SSIS SELb-S to Portuguese, the instrument was administered to 200 5th graders, along with self- and hetero-report measures of school well-being and involvement, peer acceptance, and academic achievement. We examined the SSIS SELb-Spt factorial validity and reliability, tested its correlations with external correlates, and examined the instruments' predictive validity. Results supported a three-factor structure of the scale, which included the dimensions of intrapersonal and interpersonal skills, and responsible decision-making. Correlations with external correlates were in the expected direction. Moreover, the scale predicted school involvement and later academic achievement. This study seems to corroborate and extend previous knowledge about the validity of SSIS SELb-S, offering validity and reliability evidence on the scale's three-factor structure.