BACKGROUND: Inappropriate lifestyles have been responsible for the leading causes of mortality. The purpose of the Fantastic Lifestyle Questionnaire is to help physicians involved in health prevention to identify and assess their patients’ lifestyles. OBJECTIVE: To translate and validate the Fantastic Lifestyle Questionnaire for use with young adults. METHODS: The process of translation into Portuguese and validation consisted of four steps: 1) translation; 2) correction and semantic adaptation by professional experts (judges); 3) content validation; and 4) a final evaluation by the target population. The statistical analyses used were Cronbach’s alpha to measure internal consistency reliability, intra-class correlation coefficient (R) for external consistency, and the Kappa index to test construct validity. RESULTS: Cronbach’s alpha coefficient measured the correlation between items and the total was 0.69, which is considered reasonable for an instrument designed to evaluate a latent variable that can only be estimated and not measured. When the items were grouped into domains, it was possible to verify that they all contributed equally to the stability of the questionnaire (α=0.60). The external consistency evaluated by intra-class correlation was R=0.92 (p=0.2), which demonstrates a high degree of reproducibility; the construct validity of 4 and 3 categories was 75 and 80.7% with Kappa indices of 0.58 and 0.7, respectively, which show an excellent discriminatory classificatory capacity. CONCLUSION: The Fantastic Lifestyle Questionnaire has an adequate internal and external consistency for evaluating young adult lifestyles, and it can be recommended for primary care and epidemiological studies.