BACKGROUND Medical students are under constant stress due to demanding academic load, fear of exam failure and hectic schedules. These factors can lead to poor sleep quality among medical students. Sleep quality of medical students not only determine their academic performance but is also important in determining long term effect on cognitive, psychosocial, behavioural as well as physical health of individuals. Although there are not enough recent studies to assess sleep quality of students, it is necessary to evaluate the condition of sleep among students. This study aims to find out the prevalence of poor sleep quality among medical students. METHODS This descriptive cross-sectional was conducted among undergraduate medical students of Kathmandu Medical College from October to November 2019 after taking ethical clearance from Institutional Review Committee of a tertiary care hospital before collecting data from participants. Subjects were recruited by simple random sampling from students of first, second, third and final years and were asked to fill the self-reported questionnaires, using Pittsburgh Sleep Quality Index. Descriptive statistical analysis was done using Statistical Software for Social Sciences version 24. RESULTS Out of 217 selected medical students, 96 (44.23%) of students have poor sleep quality with prevalence among male and female students as 41 (39.8%) and 55 (48.2%) respectively. The mean duration of sleep among students was 6.7±1.6 hours. CONCLUSIONS Significant numbers of medical students have poor sleep quality which may affect their academic performance and may have long term impact on their health. Efforts must be directed towards educating about the sleep hygiene as well as proper time management skills.