Background: Identification of complications or death risk factors in patients with acute poisoning allows better monitoring and treatment. Hence, the aim of this study was to determine the relative risk of toxico-clinical parameters based on poisoning severity and outcomes in patients with acute poisoning. Methods: This cross-sectional study consisted of patients with acute poisoning admitted to the poisoning emergency room from 2018 to 2019. Patients were categorized into four groups minor, moderate, severe, and fatal poisoning. Different toxico-clinical parameters were analyzed by multivariate logistic regression. Results: The most common poisoning in the minor group was opioids, alcohols, and benzodiazepine (14.7%), in the moderate and severe groups was multidrug (23.3%) and in the fatal group pesticides poisoning (23%). Pre-hospital antidote administration (OR, 7.08; P-value, 0.006); low level of consciousness (OR, 4.38; P-value, 0.001); abnormal ECG (OR, 4.56; P-value, 0.003); and time interval of intoxication to admission in the hospital (OR, 1.15; P-value, 0.01) were the predictive factors for poisoning severity. 49.7% of patients recovered without any complications. Patients with low level of consciousness (OR, 66.06; P-value, 0.01); underlying disease (OR, 3.65; P-value, 0.03); abnormal respiration (OR, 1.14; P-value, 0.02); and longer duration of hospitalization (OR, 1.02; P-value, 0.001) had greater risk of complications/ Death. Conclusions: In clinical practice, low level of consciousness, pre-hospital antidote administration, abnormal ECG, underlying disease, abnormal respiration, delay to presentation to hospital, and longer length of hospital stay can be considered important factors for determining poisoning severity and outcome.