This study examined cortical alpha power during quiet and dual-task standing in older adults with mild cognitive impairment (MCI) and cognitively intact older adults using electroencephalography (EEG). Participants completed quiet standing and dual-task standing while EEG and postural sway were recorded. Older adults with MCI exhibited greater decreases in alpha power during dual-task standing, and lower alpha power was associated with greater postural sway. These findings suggest that alpha oscillations may serve as a neurophysiological biomarker of impaired postural control and motor-cognitive decline, with potential implications for fall risk assessment and future interventions such as non-invasive brain stimulation.