Background Positive psychotic symptoms of schizophrenia are generally characterized by hallucinations and delusions. We propose to assess the relationship between total composite trauma and positive psychotic symptoms, along with the mediation effect of cognition, fear of COVID-19, insomnia, anxiety, distress, and depression of Lebanese patients with schizophrenia. Methods A cross-sectional study was carried out, between June and July 2021, by deriving data from 155 long-stay in-patients diagnosed with schizophrenia. Results Depression, anxiety, and distress but not cognitive impairment, insomnia, and fear of COVID-19) mediated the association between lifetime traumatic experiences and positive psychotic symptoms. Higher traumatic experiences were associated with greater depression, anxiety, and distress, indicating a significant positive total effect on positive psychotic scores. Moreover, higher depression, anxiety, and distress were significantly associated with higher positive psychotic symptoms. Conclusion Our results contribute to the existing knowledge by suggesting other possible intervention paths through mediating factors. Interventions that improve anxiety, depression, and distress severity may be effective in reducing positive psychotic symptoms among patients with schizophrenia having experienced lifetime trauma.