Worldwide, nurses have been reporting high levels of burnout. Given the high prevalence of nurse burnout, measurements of burnout need to be carefully considered for their validity and reliability. Our research team used a relatively new instrument to measure burnout among nurses: the Copenhagen Burnout Inventory (CBI). This 19-item instrument measures burnout in three dimensions: Personal, Work-related, and Client-related Burnout. However, the psychometric properties of the CBI have not been examined in nurses. Thus, the purpose of this study was to determine the psychometric properties of the CBI in a state-wide survey of inpatient staff nurses. A total of 928 registered nurses working in Alabama-area hospitals (N = 42 hospitals) participated in this study. Confirmatory factor analysis resulted in an adequate fit to the data and supported construct validity. As evidence of convergent validity, the CBI was moderately to highly correlated with measures of the overall work environment, job satisfaction, and intent to leave, in the anticipated directions. The Cronbach's alphas for Personal Burnout, Work-related Burnout, and Client-related Burnout were 0.91, 0.89, and 0.92, respectively, demonstrating excellent internal consistency reliability for the subscales. Based on our data, the CBI demonstrates adequate validity and reliability for measuring burnout among frontline nurses. As nurses provide care to the most vulnerable patients in healthcare systems, their psychological well-being is important due to the impact on quality of care on patient outcomes. The availability of the CBI on its website allows nurses, nurse managers, and researchers to evaluate burnout in a variety of nursing populations with no licensing costs.