Most studies investigating genetics of dementia have focused on Alzheimer’s disease, but little is known about the genetics of vascular dementia (VD). The aim of this study was to identify the association between Apolipoprotein E4 (Apo E4) genotype and VD in cerebrally infarcted patients. The study was conducted on 100 patients with cerebral infarction: 50 had VD (cases) and 50 didn’t have dementia (controls). Diagnosis of VD was based on Mini-Mental State Examination, Cambridge Cognitive Examination (CAMCOG), the Diagnostic and Statistical Manual of Mental Disorders 4th edition criteria for the diagnosis of VD (DSM-IV), Hachinski Ischemic Score, and computed tomography of the brain (CT brain). Apo E4 allele was assessed through DNA genotyping. The study showed that hypertension (p = 0.027, OR = 4.71), diabetes mellitus (p = 0.003, OR = 6.05) and Apo E4 allele (p = 0.017, OR = 13.39) were the independent risk factors of VD among studied participants. The study concluded that cerebrally infarcted patients with Apo E4 genotype are at high risk of developing VD.