Glucose transporter type 1 (GLUT1) deficiency syndrome is a metabolic disorder characterized by a low cerebrospinal fluid glucose level caused by decreased activity of the glucose transporter protein. Of approximately 100 patients described with this syndrome in the published literature to date, only 3 patients have had intermittent ataxia as the initial manifestation. This case report describes a 13-year-old boy with a longstanding history of intermittent ataxia who was diagnosed as having GLUT1 deficiency syndrome after the onset of seizures at age 11 years. This case highlights the importance of a carefully organized lumbar puncture in the investigation and management of any child with neurodevelopmental delay and intermittent ataxia with or without seizures.