We report genetically confirmed heterozygote oculopharyngeal muscular dystrophy (OPMD) accompanied by dementia, suggesting a possible causal association between OPMD and dementia. The proband first noticed bilateral ptosis, dysphagia, and proximal dominant muscle weakness in the lower extremities at age 53. Ten years later, she was found to have dementia with a score of 10/30 on the mini-mental state examination (MMSE). On PABPN1 gene analysis, the GCN repeat was expanded 17 times in one allele. In addition, the proband's younger brother exhibited myopathy and dementia. To our knowledge, this is the first report of genetically confirmed heterozygote OPMD associated with dementia.