Background: Sleep quality has significant effects on cognitive performance and physical power and is influenced by multiple factors such as stress. Contrary to the ideal, medical students suffer from sleep deprivation and stress at times when they should achieve the greatest amount of learning. However, poor sleep quality may negatively impact test performance as well, creating a vicious circle. Aim of the study: this study aimed to assess the relationship between sleep quality and academic performance among medical students in Taif University. Methods: this descriptive, cross-sectional analytic study was conducted on 299 of Saudi male and female medical students in Taif University, Saudi Arabia, who completed a self- administered survey by using the Pittsburgh Sleep Quality Index (PSQI) and academic grades to collect data. Data were collected from 5-Feb-2017 to 28-May-2017.The analysis was performed using IBM SPSS statistics (v. 23). Results: a total of 299 medical students were included in this study and surveyed to check for any association between the quality of sleep and their academic scores. Almost 56% of the participants were females. The highest percentage of the participants were from 3rd year (30.4%) and the least were from the fifth year who represented only 9.4%. the highest percentage of the participant had academic score between 3-3.5 and represent 36.5%, while those who scored between 3.5 and 4 represented 34.8% of the group. The least were those who scored 2 or less they were only 5 students (1.7%). The average sleep score for all the participants was 14.17(SD±2.7). There was a significant difference in the sleep score between males and females (p value =0.04). The Females scored higher (14.46±2.7) than the males (13.82±2.7) which means that the fames had slightly better sleep quality. There was no significant difference in sleep quality between student from different academic years (p value = 0.97) and between students of different academic achievement (p value=0.99). There is no significant correlation between the score representing the Quality of sleep and the academic score (p value =0.935). Conclusions and recommendation: the sleep quality was negatively associated with academic performance in medical students. Health education is recommended to improve quality of sleep and promoting lifestyles of the students.