Introduction: Medical students are a subgroup of the general population who are more vulnerable to poor sleep quality. Objectives: To assess the sleeping pattern and determinants among the medical undergraduate students of a Government teaching Hospital, Kolkata. Materials and Methods: An Institution-based cross-sectional study was conducted among 293 undergraduate medical students of a teaching Hospital of Kolkata from October 2017 to December 2017 using a pre-designed, pre-tested structured questionnaire, Pittsburgh Quality of Sleep Index (PSQI) score and Epworth Daytime Sleepiness Scale (EDSS). Results: About 24.91% of students had daytime sleepiness as per Epworth Daytime Sleepiness Scale (EDSS) and about 63.48% had poor sleep quality as per Pittsburgh Quality of Sleep Index (PQSI) score. There was significant correlation between Poor Sleep Quality (PSQI) score and age, year of study, hostel residence, socio-economic condition, body mass index, smoking, alcohol intake, caffeine consumption, exercise, stress and excessive use of mobile/laptop. EDS score was significantly associated with age, semester of study, residence and habit of exercise. Conclusion: To improve the sleep quality of medical students, we should provide a positive environment by establishing counselling facilities and promoting good sleep hygiene.