Health-related stigma is a common phenomenon worldwide. The stigma associated with mental illness is widespread. Stigma is an important barrier to mental health treatment and recovery. Aim: This study aims to determine level of internalized stigma of mentally ill patients and to identify factors associated with high level of internalized stigma of mentally illness. Study Design: quantitative descriptive cross sectional study was used. Setting: This study was carried out at National Center for Mental Health-Fhais Hospital-Jordan. Sample: convenient sample (All available patients with depressive disorders, bipolar mood spectrum disorders, and schizophrenia spectrum disorders. at age of 18 years and above. An estimated sample size was estimated about 105 patients which represents approximately of the total number of patient in National Center for Mental Health-Fhais Hospital). Data collection tool: Data was collected through a structured Interviewing questionnaire which composed from two parts. First Part: Personal Health Questions Second Part: Internalized Stigma of Mental Illness Scale. Results: One hundred and five participants participated in the study. The majority of them aged between 15-45 years old and only 22.9% of them were between 46-60 years old. Overall, stigma total score was also closed to the middle point. The intercorrelation between stigma domains it is evident that the first four domains (alienation, stereotype endorsement, discrimination experience, and social withdrawal) had a significant correlation with the stigma total score. Conclusion: Internalized stigma is a major problem among persons with mental illness at National Center for Mental Health-Fhais Hospital-Jordan. Internalized stigma has the potential to substantially affect adherence to medication and is likely to affect the recovery process.