ABSTRACT Objective: to validate an educational booklet for the promotion of knowledge about the prevention of Metabolic Syndrome in adolescents. Method: a time series quasi-experiment conducted in 2020 with 37 adolescents from five public schools belonging to the teaching state network of Picos, Piauí, Brazil. It was conducted in two phases: 1) development of a script of questions about the prevention of MS and its content validation by 17 experts; 2) quasi-experiment with reading of the booklet called “Síndrome Metabólica: Como me prevenir?” (“Metabolic Syndrome: How can I protect myself?”, and assessment of the adolescents' knowledge through a script of questions before and after reading the booklet. To analyze content validity of the script of questions, the Content Validity Ratio was calculated (CVR>0.529). The McNemar test (p<0.05) was used to investigate the effect of the educational booklet on the adolescents' knowledge. The study was approved by the Research Ethics Committee of Universidade Federal do Piauí. Results: the script of question's overall CVR was 0.718, representing good content validation. Three assertions were removed (CVR<0.529). Regarding the adolescents' knowledge, 45.9% improved it, with no significant difference (p=0.067). Conclusion: the adolescents' knowledge was higher in almost half of the participants in the post-test, showing that reading the educational booklet favored knowledge about the prevention of Metabolic Syndrome.