Purpose: Alcohol is one of the most commonly co-ingested agents in deliberate self-poisoning (DSP) cases presenting at the emergency department (ED). The increased impulsivity, aggressiveness, and disinhibition caused by alcohol ingestion may have different clinical features and outcomes in cases of DSP. This study investigates whether alcohol co-ingestion affects the clinical features and outcomes of DSP patients in the ED. Methods: This was a single-center retrospective study. We investigated DSP cases who visited our ED from January 2010 to December 2016. Patients were classified into two groups: with (ALC+) or without (ALC–) alcohol co-ingestion. The clinical features of DSP were compared by considering the co-ingestion of alcohol, and the factors related to discharge against medical advice (AMA) of DSP were analyzed. Results: A total of 689 patients were included in the study, with 272 (39.5%) in the ALC+ group. Majority of the ALC+ group patients were middle-aged males (45-54 years old) and arrived at the ED at night. The rate of discharge AMA from ED was significantly higher in the ALC+ group (130; 47.8%) compared to the ALC– group (p=0.001). No significant differences were obtained in the poisoning severity scores between the two groups (p=0.223). Multivariate analysis revealed that alcohol co-ingestion (odds ratio [OR]=1.42; 95% confidence interval [CI], 1.01-1.98), alert mental status (OR=1.65; 95% CI, 1.17-2.32), past psychiatric history (OR=0.04; 95% CI, 0.01-0.28), age >65 years (OR=0.42; 95% CI, 0.23-0.78), and time from event to ED arrival >6 hrs (OR=0.57; 95% CI, 0.37-0.88) were independent predictive factors of discharge AMA (p=0.043, p=0.004, p=0.001, p=0.006, and p=0.010, respectively). Conclusion: Our results determined a high association between alcohol co-ingestion and the outcome of discharge AMA in DSP patients. Emergency physicians should, therefore, be aware that DSP patients who have co-ingested alcohol may be uncooperative and at high risk of discharge AMA.