Background: Burnout is clinically significant because it has adverse consequences in the form of mental and physical illnesses and economic losses. The goal of the research study was to translate the Copenhagen Burnout Inventory (CBI) into Slovak and then assess its factor structure, reliability, validity, and psychometric properties. Methods: We collected two convenience samples: one for the psychometric properties analysis and factor analysis, which consisted of 4789 participants, and the other for the validity analysis, which consisted of 458 participants. Data were collected online. The participants filled out the following questionnaires: Copenhagen Burnout Inventory (CBI), Oldenburg Burnout Inventory (OLBI), Professional Quality of Life Scale (PROQOL), and Secondary Traumatic Stress Scale (STSS). Results: The CBI had very good reliability in both samples, calculated using Cronbach alpha coefficients (between 0.839 and 0.908). In terms of CBI validity, all the correlation coefficients between the scale and subscales were between moderately high and high and ranged from 0.505 to 0.859. Except for two items, CBI7 and CBI10, all the items fall into the original factors of the scale. Conclusions: The Slovak version of the Copenhagen Burnout Inventory is a statistically sound instrument with high coefficients of reliability as well as validity and has an acceptable factor structure.