Background: Remimazolam is a novel benzodiazepine anesthetic increasingly used for total intravenous anesthesia (TIVA); however, its electroencephalographic signatures—especially in elderly patients—remain poorly characterized. This study aimed to evaluate the relationship between age and intraoperative electroencephalogram (EEG) dynamics during remimazolam-based TIVA. Methods: This prospective observational study analyzed EEG recordings from 69 adult patients receiving remimazolam-based TIVA. We conducted linear regression and Pearson correlation analyses to assess the correlation between age and intraoperative EEG components, including absolute and relative power of EEG frequency bands, frontal coherence, aperiodic components, burst suppression ratio, patient state index (PSI), and spectral edge frequency. Results: Absolute alpha (r = −0.412, P < 0.001), beta (r = −0.459, P < 0.001), and gamma power (r = −0.372, P = 0.002) decreased with age. Conversely, relative delta (r = 0.297, P = 0.013) and theta power (r = 0.433, P < 0.001) increased with age, whereas relative alpha (r = −0.354, P = 0.003) and beta power (r = −0.266, P = 0.027) decreased with age. Frontal coherence of delta (r = −0.436, P < 0.001), theta (r = −0.279, P = 0.02), alpha (r = −0.269, P = 0.025), and beta (r = −0.27, P = 0.025) oscillations decreased with age. Conclusions Older patients exhibited decreased alpha and beta powers, increased delta and theta dominance, and decreased frontal coherence under remimazolam anesthesia guided by the PSI. These findings suggest age-specific alterations in cortical dynamics that may affect EEG monitoring during remimazolam anesthesia.