An 11-year-old autistic girl was admitted to the Emergency Room for a self-resolving episode of seizure. An electroencephalogram (EEG) under sedation was easily performed with the administration of intramuscular dexmedetomidine. Patients with autism spectrum disorder are difficult to manage, even when they undergo non-invasive painless procedures that need a minimal collaboration, such as EEG study, so sedation may be required. A growing literature has been showing the efficacy and safety of dexmedetomidine sedation in EEG. This case report highlights the safety and efficacy of this therapeutic option in children with neurobehavioral disorders in the Emergency Room setting.