We evaluated the ability of the ethanol extract of red ginseng (RGE) to regulate sleep architecture. Adult rats were chronically fitted with sleep–wake recording electrodes. Following post-surgical recovery, rats were habituated extensively to freely moving polygraphic recording conditions. Polygraphic signs of undisturbed sleep–wake activities were recorded for 12 h after RGE administration. Ginseng treatment produced more time in non-rapid eye movement (NREM) sleep and total sleep. The total percentage of wakefulness decreased comparably, and the number of sleep–wake cycles was reduced after 10 and 50 mg/kg RGE. RGE (10 mg/kg) administration decreased the power density of cortical electroencephalogram (EEG) δ-waves (0.75–4.5 Hz) and increased α-waves (8.0–13.0 Hz) in NREM and rapid eye movement (REM) sleep. It also decreased δ-wave power density during wakefulness. Although 100 mg/kg RGE showed little effect on the power densities in NREM and REM sleep, it increased δ-wave and decreased θ-wave (5.0–9.0 Hz) power densities during wakefulness. Thus, RGE increases spontaneous sleep and NREM sleep. Regulation of sleep architecture by RGE involves decreased δ- and θ-wave and increased α-wave activities according to cortical EEG.