The study aimed to accomplish a cross-cultural adaptation of the 'Diabetes - 39 - D-39' instrument for Brazil, to test the validity of the adapted version in a sample of type 2 diabetes mellitus patients and to describe the participants of the study, according to the scores obtained on the Likert-type scale. The instrument adaptation process followed several steps: instrument translation; achievement of the consensus in Portuguese; evaluation by an expert committee; back-translation; achievement of the consensus in English; comparison of the original and consensus versions in English; semantic analysis and pre-test of the Portuguese version. Results showed that the instrument items, in the first stage of cultural adaptation to Portuguese, presented high internal consistency levels.