RESUMEN
Abstract Background The Brief Negative Symptom Scale (BNSS) assesses the presence and intensity of negative symptoms in schizophrenia. Objectives This study aimed to carry out the BNSS cross-cultural adaptation to the Brazilian Portuguese language and verify its content validity and reliability. Methods This is a methodological study that followed these steps: (1) implementation of the cross-cultural adaptation and translation protocol, (2) BNSS adapted content validation, and (3) reliability assessment. Six experts participated in the adaptation process. The sample consisted of 30 individuals diagnosed with schizophrenia and assisted at the Brazilian Psychosocial Care Center (CAPS), in João Pessoa, Paraíba, Brazil, which was the research setting. Results The cross-cultural adaptation was successful due to the values obtained for each aspect evaluated, such as semantic (0.922), idiomatic (0.910), experiential (0.961), and conceptual equivalence (0.974). The same happened with content validity regarding clarity of language (0.935), practical relevance (0.974), and theoretical relevance (0.948). Cronbach's alpha coefficient was 0.884 for the entire instrument, and the items ranged from 0.865 to 0.882. Discussion The BNSS adaptation process has shown to be satisfactory for use in the Brazilian context, constituting a useful clinical tool for teaching and research.