Objectives: This study explored criminal thinking styles and feelings of aggression and hopelessness among male and female inmates who reported mental disorders and those who did not. Methods: A total of 4,204 respondents (3,986 males and 218 females) who were expected to be released from prison within 24 months completed an hour-long audio computer-assisted self-interview survey that included the Beck Hopelessness Scale, Buss-Perry Aggression Questionnaire Short-Form, and Criminal Sentiments Scale-Modified. Weights were constructed to adjust the sampled population to the full population of the prison. Results: A mental disorder was reported by 19.8% of male and 46.1% of female participants, with 6.6% of males and 19.4% of females reporting a serious mental disorder. The criminal thinking patterns of male and female inmates who reported mental disorders were consistent with those of inmates who reported no mental disorders; however, levels of criminal attitudes were significantly higher among males reporting serious mental disorders than males reporting other mental disorders or no disorders. Inmates reporting mental disorders scored significantly higher on measures of aggression and hopelessness. Conclusions: Results of this study suggest that inmates who report mental disorders have anti-social attitudes consistent with inmates who do not report mental disorders but have levels of aggression and hopelessness that are higher than their counterparts who do not report mental disorders. These findings are vital to the development of evidence-based interventions that respond accurately and holistically to the complex constellation of needs among persons with mental disorders who are involved in the justice system.