The aim of this study was to evaluate the reliability and validity of the Turkish version of the Internalized Stigma of Mental Illness Scale (ISMI) in patients with psychiatric disorders.The study included 203 patients diagnosed with various psychiatric disorders in a psychiatry outpatient clinic of a university hospital. The reliability of the scale was assessed by investigation of its internal consistency and split-half reliability. The convergent validity of the scale was demonstrated by the relationship between the Turkish form of the ISMI and various criteria scales.Cronbach's alpha value was 0.93 for the entire scale and ranged between 0.63 and 0.87 for the 5 subscales of the ISMI. In terms of convergent validity, the total score of the Turkish ISMI significantly correlated with the Beck Depression Inventory, Rosenberg Self-Esteem Scale, Sociotropy-Autonomy Scale, Brief Symptom Inventory, Multidimensional Scale of Perceived Social Support, Clinical Global Impression Scale, and Global Assessment of Functioning Scale scores. All values were in the expected direction.In the light of the findings, it was concluded that the Turkish version of ISMI could be used as a reliable and valid tool in assessing internalized stigma of the Turkish psychiatric patients.