Background: Clozapine is a psychiatric medication that may cause various side effects, some of them may be serious and fatal adverse effects, such as severe neutropenia, agranulocytosis, lymphocytopenia, myocarditis, and orthostatic hypotension, that have been associated to an increased risk of death. Objective: This study aimed to evaluate the serious and potentially fatal adverse effects of clozapine toxicity in psychic patients at mental health care hospitals in the Southern region of the Kingdom of Saudi Arabia. Methods: By using a survey, data were retrospectively collected from 193 adult psychic patient reports who have been administrated clozapine with regular follow-ups, in mental health hospitals in the Southern region of Saudi Arabia between 2019 and 2021. Then, these data are recorded and analyzed Statistically using SPSS software, with suitable tests, and predetermined statistical significance (p-value) of less than 0.001. Results: The occurrence of agranulocytosis, neutropenia, hypotension, and seizures showed a highly significant correlation with higher doses of clozapine administration (i.e. p < 0.001). Similarly, agranulocytosis and neutropenia were significantly associated with the occurrence of both hypotension and seizures (i.e. p < 0.001). Conclusion: The collected data in this study showed an increased incidence of agranulocytosis and neutropenia associated with clozapine-treated psychic patients in the Southern region of the Kingdom of Saudi Arabia which warrants further clinical studies to find this correlation.