Introduction: The quality of sleep refers to the fact that we sleep well at night and daytime functioning. Thus, influences health and quality of life. Sleep loss is one of the most striking problem of modern society especially in medical students. This is related to the constant academic demands causing mental health problems and high levels of stress. Methods: A cross-sectional study. We evaluated 1,040 medical students in 8 universities of Peru from the first to the sixth year of study. Of these, 892 surveys were used. Mental health were evaluated according to the scale of Depression, Anxiety and Stress (DASS-21) and "poor sleepers" students were established with a score ≥ 5 according to the Pittsburgh Sleep Quality Index (PSQI). Results: It was found that 693 (77.69%) students were poor sleepers. About mental health was found that 290 (32.51%) suffered from depression, 472 (52.91%) of anxiety and 309 (34.64%) stress. A significant association (p < 0.05) was found between poor sleep quality and female sex (OR = 1.13, CI = 1.05 to 1.21); depression (OR = 1.23, CI = 1,15-1,31); anxiety (OR = 1.32, CI = 1.23 to 1.43); and stress (OR = 1.26, CI = 1.19 to 1.35). Conclusion: We observed a high frequency of poor sleepers in medical students from eight universities of Peru. The poor quality of sleep was associated with anxiety, depression and stress in students of second and third year, respectively.