Purpose: To understand the multiple signs of Horner syndrome and to recommend protocols for pediatricians to obtain an accurate diagnosis of Horner syndrome. Methods: The medical records of 17 pediatric patients with Horner syndrome, neonates to eighteen years of age, were collected and analyzed. Data recorded included age, presenting symptoms, other medical history, allergies, medications, pupil size, presence of anhidrosis, and presence of ptosis. From the available pupil sizes, average degree of anisocoria was calculated. Results: All 17 patients had other clinical findings of Horner syndrome in addition to anisocoria. On initial evaluation, 100% had ptosis and 25% had anhidrosis. Of the available pupil size data, the average level of anisocoria was 2.06 mm, with a standard deviation of 1.17 mm. Conclusion: Physicians are reminded to measure pupil size to determine the degree of anisocoria when present, as it may help distinguish benign conditions from underlying pathology. Educating pediatricians on measurement of anisocoria and additional signs of Horner syndrome will help with proper referral patterns.