Mental health illnesses are increasing in severity and number among medical students. This study aims to estimate the prevalence of mental disorders among medical students and their associated factors. Nine hundred students were selected from Mansoura Faculty of Medicine by the cluster sampling method. Data were collected using an Arabic self-administered questionnaire and the Arabic version of the Symptoms Checklist 90 Revised. Both bivariate and multivariate logistic regression analyses were done. Approximately 59% of students had one or more mental disorders. The prevalence of high Positive Symptom Distress Index (PSDI), depression, and somatization was 30.1%, 25.2%, and 21.7%, respectively. Logistic regression revealed that being male, younger than 20 years age, living away from family, rural families, and very low or low social class were independent risk factors for most of the mental disorders studied. In conclusion, mental disorders were common among medical students. Mental health care should be mandatory for these students.