In Turkey, prison studies are rare and the mental health status of prisoners has not received proper attention. The purpose of this cross-sectional and descriptive study was to assess the prevalence of depression, anxiety, stress, and anger among a group of Turkish prisoners. Two self-reporting instruments (the Depression Anxiety Stress Scale-42 and Multidimensional Anger Scale) were filled out by 685 prisoners. Prisoners in the study group were found to be depressive, anxious, and stressed. Anger symptoms and aggressive behaviors were found to be at a moderate level. Prisoners with a history of being subjected to domestic violence in childhood had higher depression, anxiety, and stress scores than those without such a history. Young prisoners, those who had been previously imprisoned, with substance dependency and higher stress and anxiety levels reported more anger symptoms than others. Psychological support, together with stress and anger management programs, seems to be essential.