Purpose: This study was performed to identify risk factors associated with post-tonsillectomy hemorrhage (PTH)-related hospitalization in pediatric patients visiting an emergency department (ED). Methods: We retrospectively reviewed the medical records of patients who underwent tonsillectomy at a single children’s hospital ED from January 2009 through December 2020. Data were collected on patient demographics, chief complaints, surgical methods, postoperative days, initial vital signs, and laboratory findings. The study population was divided into hospitalized and discharged groups. Results: Among a total of 2,716 patients reviewed, 67 met the inclusion criteria. The hospitalized group showed a lower median systolic blood pressure (108.0 [interquartile range, 82.0-134.0] vs. 118.5 [89.8-147.2] mmHg; P = 0.021) and a faster median respiratory rate (23.0 [18.0-28.0] vs. 20.0 [17.0-23.0] breaths/minute; P = 0.019), compared with the discharged group. Multivariable logistic regression identified systolic blood pressure under 100 mmHg (odds ratio, 5.21; 95% confidence interval, 1.17-37.60) and respiratory rate over 24 breaths/minute (7.31; 1.07-145.79) as the factors associated with PTH-related hospitalization. Conclusion When pediatric patients visit EDs for PTH, close monitoring or hospitalization may be needed in those with low systolic blood pressure or rapid respiratory rate.