The objective of this study was to investigate high-frequency conductivity (HFC) obtained using magnetic resonance electrical property tomography (MREPT) in participants with Alzheimer’s disease (AD), amnestic mild cognitive impairment (MCI), and cognitively normal (CN) elderly controls. High-frequency conductivity (HFC) values in the brain are significantly increased in Alzheimer’s disease (AD) patients compared to cognitively normal (CN) elderly people, are negatively associated with Mini-Mental State Examination (MMSE) scores, and therefore can be used as an imaging biomarker to improve the differentiation of AD from CN.