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This study aimed to investigate the relationship between daytime sleepiness and mortality risk among older adults. The moderating effects of sex and physical function were examined. This 9-year follow-up study was conducted with community-dwelling individuals aged ≥65 years. Daytime sleepiness was evaluated using the Epworth Sleepiness Scale (ESS). Exploratory factor analysis (EFA) was used to examine the ESS factors. Handgrip strength was measured to assess physical function, and the highest quartile was defined as good muscle power. Cox regression analysis was used to estimate the 9-year all-cause mortality risk. The interaction terms were examined to evaluate their moderating effect. In total, 2588 individuals participated in the study. The EFA explored two factors: the passive factor (PF) and the active factor (AF). After controlling for various covariates, the cutoff-defined daytime sleepiness (ESS≥11), total raw scores, and factor scores of the ESS all failed to predict mortality risk. The 3-way interaction terms showed statistical significance in terms of [sex × PF × muscle power (p = 0.03)] but not for [sex × AF × muscle power (p = 0.11)]. Specifically, PF predicted mortality risk in women with good muscle power (hazard ratio (HR): 1.48; 95 % confidence interval (CI): 1.04–2.10), which is female-specific. In contrast, AF predicted mortality risk only in men with good muscle power (HR: 1.35; 95 % CI: 1.02–1.78). The ESS-measured daytime sleepiness in older adults is multidimensional. The mortality risk for each dimension was determined based on sex and physical function. • The Epworth Sleepiness Scale (ESS) had dual construct in older adults. • Sex- and muscle power modified mortality risk conferred from daytime sleepiness. • Dimensions of the ESS conferred sex-specific mortality risk. [ABSTRACT FROM AUTHOR]