Objective: The Brief Negative Symptom Scale (BNSS) is an instrument for evaluating negative symptoms (NS) in schizophrenia based on the 2005 consensus statement by the National Institute of Mental Health. This study examines the validity and reliability of the Danish version of BNSS. Materials and methods: Acutely and chronically affected patients with schizophrenia or schizoaffective disorder were assessed with BNSS along with other psychopathological scales and clinical measures. Convergent and discriminant validity of BNSS was evaluated by its relationships with these assessments. Inter-rater agreement was estimated by the intraclass correlation coefficient (ICC). Results: Forty-nine subjects were included; the mean age was 33.1 (±10.8) years and 32 (65%) were males. BNSS correlated strongly with traditional assessment tools for NS and poorly with measures of depressive and extrapyramidal symptoms, except for Parkinsonism. Moreover, BNSS correlated well with the assessment of positive symptoms. The ICC of BNSS was 0.95 (n = 19, 95% CI: 0.88-0.98). Conclusions: Overall, BNSS holds appropriate psychometric properties in terms of reliability and validity. However, discriminant validity was compromised by correlations with positive symptoms and Parkinsonism. The former originates presumably from NS secondary to positive symptoms since the sample included acutely psychotic patients, and the latter from overlapping rating criteria regarding facial expressivity impairment.