Purpose: This study examined the clinical and epidemiological characteristics of intensive care unit (ICU) patients admitted or died in the emergency medical center with acute-poisoning to investigate the variables related to the prognosis. Methods: The data were collected from poisoning patients admitted or died in the emergency medical center of a general hospital located in Seoul, from January 2014 to February 2020. The subjects of this study were 190 patients. The medical records were screened retrospectively, and the clinical and epidemiological characteristics of the patients in the emergency room (ER) and ICU were examined to investigate the contributing factors that influence the poor prognosis. Results: The study analyzed 182 patients who survived after being admitted to the intensive care unit (ICU). The results are as follows. The mental change (87.4%) was the most common symptom. Sedative poisoning (49.5%) was the commonest cause. For most patients, pneumonia (26.9%) was the most common complication. Hypotension (23.7%), tachycardia (42.1%), fever (15.8%), seizures (10.5%), dyspnea (2.6%), high poisoning severity score (PSS), type of toxic material, mechanical ventilator application (39.5%), inotropes application (39.5%), and pneumonia (55.3%) were correlated the LOS over 5 days in the ICU. 8 patients died. In the case of death pesticides and carbon monoxide were the main toxic materials; tachycardia, bradycardia, and hypotension were the main symptoms, and a mechanical ventilator and inotropes were applied. Conclusion: Patients with unstable vital signs, high PSS, and non-pharmaceutical poisoning had a prolonged LOS in the ICU and a poor prognosis.