Glut-1 deficiency syndrome (Glut-1 DS, OMIM #606777) is characterized by infantile seizures, developmental delay, acquired microcephaly and hypoglycorrhachia. It is caused by haploinsufficiency of the blood–brain barrier hexose carrier. Heterozygous mutations or hemizygosity of the GLUT-1 gene cause Glut-1 DS. We generated a heterozygous haploinsufficient mouse model by targeted disruption of the promoter and exon 1 regions of the mouse GLUT-1 gene. GLUT-1^+/− mice have epileptiform discharges on electroencephalography (EEG), impaired motor activity, incoordination, hypoglycorrhachia, microencephaly, decreased brain glucose uptake as measured by positron emission tomography (PET) scan and decreased brain Glut-1 expression by western blot (66%). The GLUT-1^+/− murine phenotype mimics the classical human presentation of Glut-1 DS. This GLUT-1^+/− mouse model creates an opportunity to investigate Glut-1 function, to examine the pathophysiology of Glut-1 DS in vivo and to evaluate new treatment strategies.