BackgroundAlcohol's effect on sleep electroencephalogram (EEG) power spectra during late adolescence is of interest given that this age group shows both dramatic increases in alcohol consumption and major sleep‐related developmental changes in quantitative EEG measures. This study examined the effect of alcohol on sleep EEG power spectra in 18‐ to 21‐year‐old college students.MethodsParticipants were 24 (12 female) healthy 18‐ to 21‐year‐old social drinkers. Participants underwent 2 conditions: presleep alcohol and placebo, followed by standard polysomnography with comprehensive EEG recordings.ResultsAfter alcohol, mean breath alcohol concentration at lights‐out was 0.084%. Interaction effects indicated simultaneous increases in frontal non‐rapid eye movement sleep (NREM) delta (p = 0.031) and alpha (p = 0.005) power in the first sleep cycles following alcohol consumption which was most prominent at frontal scalp sites (p < 0.001). A decrease in sigma power (p = 0.001) was also observed after alcohol.ConclusionsAs hypothesized, alcohol increased slow wave sleep‐related NREM delta power. However, there was a simultaneous increase in frontal alpha power. Results suggest that alcohol may exert an arousal influence which may compete with the sleep maintenance influence of increased delta activity. The phenomenon is similar to, or the same as, alpha‐delta sleep which has been associated with the presence of disruptive stimuli during sleep. This may have negative implications for the impact of presleep alcohol consumption on sleep and consequent daytime functioning.