Background: The purpose of this study is to develop and validate the Korean dysfunctional depression scale, which measures pathological depression including subclinical depression and clinical depression. Methods: To achieve this purpose, we collected data from patients diagnosed as having depressive disorder and clients with chief complaints related to depression, and 360 data were analyzed. Results: Using item linkage methods, we decided 20 items as a dysfunctional depression scale for group research. The results of reliability verification show high internal consistency and stable test-retest reliability. In addition, the result of factor validity demonstrates general factor and two specific factors-the first specific factor is 'the physical-somatic factor' and the second specific factor is 'the pessimistic cognition and alienation factor'. Convergent validity was also confirmed good. Lastly, this study performed standard setting workshop consisting of content experts to decide cut-scores of dysfunctional depression scale. Through the workshop, the standard cut-score of normal-subclinical depression was decided as 44 and the standard cut-score of subclinical-clinical depression was decided as 58. The classification consistency and accuracy indices were to validate standard cut-scores. Conclusions: This Korean dysfunctional depression scale is verified to have high reliability and validity.