Introduction: The aim of this study was to assess the sleep quality and daytime sleepiness of resident doctors, to compare the sleep quality between surgical and medical branch residents and to examine effects of working hours, number of duties, clinical branches and some other daily habits on the sleep quality of resident doctors in a hospital in Turkey. Methods: A survey was conducted to gather data on (i) demographics, lifestyle and daily habits as well as to determine (ii) Epworth sleepiness scale (ESS) score and (iii) Pittsburgh sleep quality index (PSQI) scores of the participants. Data collection was based on the use of a self-administered questionnaire. Results: Of 138 resident doctors, 45.7% were classified as having good sleep quality based on a cut-off score of 5 in PSQI. The mean ESS and PSQI scores were 6.59 ±3.92 and 6.30 ±3.22, respectively. Significantly positive correlations were found between Epworth score and the number of night duties (p=0.010), working hours per week (p=0.006), total cigarettes per day (p=0.033), and daily tea consumption (p=0.013). Also, there were statistically significant positive correlations between PSQI scores and the number of night duties (p<0.001), working hours per week (p=0.007), total cigarettes per day (p=0.013) and daily coffee consumption (p=0.002). Surgical residents had significantly poor sleep quality (p=0.015). ESS score was higher in female residents and surgical residents, with a significant difference in these two sub-groups (p=0.018, p=0.008 respectively). Conclusions: Sleep quality and daytime sleepiness of the resident doctors were closely related to lifestyle factors including working hours, number of night duties and branch of residency as well as to certain demographic factors and daily habits.