Purpose: Aspiration pneumonia is an important complication of drug intoxication with decreased mental status. The purpose of the study is to investigate the risk factors of aspiration pneumonia in the patients of benzodiazepine overdose with or without co-ingestion of other drugs. Methods: A retrospective chart review of patients who visited the emergency department between January 2012 and December 2014 was conducted. Demographic data, time from ingestion to visit, initial vital signs, symptoms, mental status, medical history, laboratory results, chest radiological findings and co-ingested medications were recorded. Multiple logistic analyses were performed to verify the association between variables and the development of aspiration pneumonia. Results: A total of 249 patients presented to the emergency department with benzodiazepine overdose. Aspiration pneumonia had developed in 24 patients (9.6%). Univariate analysis revealed time from ingestion to visit was longer, Glasgow coma scale score was lower, hypoxia was presented, leukocytosis was shown, types of ingested drugs was high, less activated charcoal was applied and tricyclic antidepressants was taken in patients that developed aspiration pneumonia. Time from ingestion to visit (odds ratio (OR) 1.121, 95% confidence interval (CI), 1.057-1.189, p=0.000), GCS score (OR 0.724. 95% CI, 0.624-0.839, p=0.000), oxygen saturation (OR 0.895, 95% CI, 0.835-0.959, p=0.002), and co-ingestion of TCA (OR 4.595, 95% CI, 1.169-18.063, p=0.029) were identified as risk factors of morbidity of aspiration pneumonia upon multiple logistic regression analysis. Conclusion: Time from ingestion to visit, low GCS score, low oxygen saturation and co-ingestion of TCA were risk factors of the development of aspiration pneumonia in benzodiazepine overdose patients.