Abstract Introduction There is growing interest in the fields of psychiatry and psychology in investigating the relationship between personality and psychopathology. The Big-5 is a model developed to investigate five personality dimensions: Extroversion, Agreeableness, Conscientiousness, Neuroticism, and Openness. In the present study, we describe the process of translation into Brazilian Portuguese and adaptation of a free tool to evaluate the Big-5 model: The Big-5 Inventory (BFI). The instrument has 44 items with a Likert response scale ranging from 1 to 5. Objectives To translate and adapt the BFI into Brazilian Portuguese. Methods The adaptation was conducted in the following steps: 1) Translation, 2) Evaluation Committee, 3) Back-translation, 4) Pilot study, 5) Evaluation Committee, and 6) Application. The sample comprised 490 participants from various regions of Brazil. The participants’ ages ranged from 18 to 71 years, most of them had completed high school (62.9%), and the majority were women (75%). Results A model with the following fit indexes was found: χ2/df: 1.954; goodness fit index (GFI): 0.924; comparative fit index (CFI): 0.920; and root mean square error of approximation (RMSEA): 0.044. Conclusion The results are suggestive that the Brazilian version of this instrument has good psychometric properties and represent a cost-free option for investigating associations with the Big-5 in psychiatry.