Background: Bell’s palsy (BP) has been reported as a sentinel symptom for malignancy in case reports and small case series. Our objective was to quantify the risk of malignancy following the emergency department (ED) diagnosis of BP using a large retrospective cohort. Methods: We performed a cohort study using the Pediatric Heath Information System database. We included children (6 months – 17 years) from 2011 to 2020 with an ED diagnosis of BP. We excluded children with previous neurologic chronic condition or malignancy diagnosed during or prior to the index visit. Our primary outcome was diagnosis of malignancy within 60 days following the index ED visit. Secondary outcomes included rate of new oncologic diagnosis by age group, the oncologic diagnoses received, and rates of imaging, laboratory testing, and hospital admission at index visit. We compared clinical characteristics between children with and without new onset malignancy. We calculated the relative risk (RR) of new malignancy between the BP cohort and a control cohort with ED diagnosis of cough. Results: 12,272 encounters for BP from 47 hospitals were included. Demographic characteristics as well as proportions of patients undergoing imaging or laboratory evaluation at the index ED visit are shown in Table 1. 41 patients had a new oncologic diagnosis within 60 days of their index BP encounter (0.33%, 95% confidence interval [CI]: 0.25-0.45%). A cumulative incidence plot of time to new onset oncologic diagnosis after the index visit compared to the control cohort is displayed in Figure 1. The incidence of new oncologic diagnosis was higher in younger children. For age groups <2 years, 2-5 years, 6-11 years, and 12-17 years, incidences were 0.68% (95% CI 0.36-1.3%), 0.70% (95% CI 0.38-1.3%), 0.26% (95% CI 0.15-0.47%), and 0.21% (95% CI 0.12-0.37%) respectively. Primary CNS malignancy (59%) and leukemia (17.1%) were the most common oncologic diagnoses discovered. The RR of new oncologic diagnosis between the BP and control cohorts was 11.2 (95% CI 8.0-15.7). Conclusion: We found a small but potentially clinically significant rate of new onset oncologic diagnosis within 60 days after BP diagnosis in the ED, especially in children younger than 5 years. Further studies of the diagnostic utility of laboratory testing or neuroimaging and the risk of empiric steroids in children with BP are needed.