OBJECTIVES: The current study aimed to explore the relationship between subjective sleep, emotions, social support and excessive daytime sleepiness (EDS), and extract the strongest predictor of EDS in female undergraduate students. METHODS: Our subjects consisted of 168 female undergraduate students (mean age 21.64±1.66). All participants completed Epworth Sleepiness Scale (ESS), Insomnia Severity Index, Hospital Anxiety and Depression Scale, Social Support Scale, and the Munich Chronotype Questionnaire. RESULTS: There were significant associations between insomnia, anxiety, depression with EDS, but not with subjective total sleep time of workdays and freedays. Also, 23.8% (n=40) of subjects endorsed clinical levels of EDS (ESS>10). Insomnia, anxiety, and depression were higher, and social support was lower in the EDS group compared to the normal group. Finally, we explored factors that influenced EDS, resulting in anxiety and social support being the strongest predictors of EDS. Social support was the strongest predictor of EDS compared to other predictors (β=-0.276, p<0.001). CONCLUSIONS: Results suggest that social support may be important to consider in female undergraduate students who experience EDS.