Guillain-Barré syndrome (GBS) cases admitted to Canadian pediatric tertiary care centers were ascertained through active surveillance. From 1996 to 2012, 246 cases were identified, and 24 (10%) had onset ≤30 days after immunization. Annual rate of postimmunization GBS was 2.0 per 100,000 hospitalizations. Postimmunization GBS was an infrequent cause of pediatric hospitalization.