Background Suicide attempters contribute to a significant public health problem. Individuals are estimated to make up to 20 suicide attempts before committing suicide. The emergency department (ED) is the first location where suicide attempters are brought. This study investigated the factors associated with early hospitalization decisions to determine the criteria for patient hospitalization rather than psychiatric ward admission and identify measures to shorten ED length of stay (LOS). Methods This study included suicide attempters (age ≥19 years) who visited the EDs at two tertiary teaching hospitals between March 2017 and April 2020. Results A total of 414 in the hospitalization and 1,346 in the discharge groups patients were included. The mean age was 50.3 ± 20.0 years and 40.7 ± 17.0 years in the hospitalization and discharge groups (p <0.001). The mean ED LOS was 4.2 ± 12.3 and 11.4 ± 18.8 h in the hospitalization and discharge groups, respectively. In the hospitalization group, the odds ratio and confidence interval for age (1.017, 1.008–1.026), sex (male) (1.787, 1.127–2.515), consciousness (2.330, 1.653–3.266), and the Risk-Rescue Ratio Scale (RRRS) (1.273, 1.242–1.304) were calculated. A receiver operating characteristics analysis of RRRS for the decision to hospitalize suicide attempters showed a cut-off value of 42, with sensitivity, specificity, and area under the curve of 85.7%, 85.5%, and 0.924, respectively.Conclusion For suicidal attempters in the ED, the decision on medical hospitalization rather than psychiatric admission should be based on their level of consciousness and the RRRS to reduce ED LOS and crowding.