Abstract Background: Adverse childhood experiences (ACEs) and substance use disorder (SUD) are well-known risk factors for psychosis and dramatically afect schizophrenia. In this research, we aimed to measure the prevalence of adverse childhood experiences and substance use disorder in patients with schizophrenia and assess the efect of ACEs on the clinical presentation and overall functioning and the association between them and SUD in patients with schizophrenia. A cross-sectional study included a random sample of 165 schizophrenic patients who were examined by doing drug screen in urine, structured questionnaire to collect Socioeconomic characteristics, history of schizophrenia, structured clinical interview for Diagnostic and Statistical Manual of Mental Disorders-ffth edition, Positive and Negative Syndrome Scale (PANSS), Adverse Childhood Experiences International Questionnaire (ACE-IQ), World Health Organization Disability Assessment Schedule 2.0, compliance rating scale, addiction severity index ffth edition (ASI) for individuals with positive urine drug screen. Results: Only 14.4% of the studied patients had no adverse childhood experiences. The prevalence of positive substance abuse screening was 18.2%. There were statistically signifcant negative correlations between total ACE score and educational level, socioeconomic level, and the onset of schizophrenia. On the other hand, statistically signifcant positive correlations were found between the total ACE score and PANSS score and ASI score. The frst most frequent ACE was signifcantly associated with female gender, lower education levels, low and middle socioeconomic classes, lifetime substance use, smokers, and positive drug screening. Emotional neglect and contact sexual abuse were signifcantly associated with positive drug screening. At the same time, Physical abuse was signifcantly associated with both lifetime substance use and positive drug screening. Conclusion: The current study’s fndings indicate that childhood adverse experiences and substance abuse are prevalent problems in patients with schizophrenia. Given that there is an association between both issues, they may afect the symptomatology of the disorder, the prognosis, and the therapeutic plan. It is advised that a greater emphasis on and identifcation of childhood trauma and drug use disorder may be a necessary step in assessing patients with schizophrenia