Background: There are known racial and socioeconomic disparities in the use of epinephrine autoinjectors (EAI) for anaphylaxis. Objective: To measure the rates of EAI prescription filling and identify patient demographic factors associated with filling rates among patients discharged from the pediatric emergency department. Methods: This was a retrospective observational cohort study of all patients discharged from a pediatric emergency department who received an outpatient prescription for an EAI between January 1, 2018, and October 31, 2019. The rates of prescription filling were calculated, and multivariable logistic regression was performed to identify sociodemographic factors associated with prescription filling. Results: Of 717 patients included in the analysis, 54.8% (95% confidence interval {CI}, 51.1%-58.5%) filled their prescription. There were no significant associations between EAI fill rates and patient age or sex. In bivariable analysis, non-Hispanic white patients were more likely to fill EAI prescriptions compared with non-Hispanic Black patients (odds ratio [OR] 1.89 [95% CI, 1.11-3.20]), and patients with in-state Medicaid were significantly less likely to fill EAI prescriptions compared with those patients with private insurance (OR 0.69 [95% CI, 0.48-0.98]). However, after multivariable adjustment, there was no significant difference in filling by age, insurance status, or race or ethnicity. Conclusions: Only approximately half the patients had their EAI prescriptions filled after discharge. Filling rates did not vary by sociodemographic characteristics.