Objective: To determine the frequency of depression, anxiety, and stress among medical students and to compare between undergraduate and postgraduate students. Study Design: Comparative cross-sectional study. Place and Duration of Study: Pak Emirates Military Hospital Rawalpindi, Public Sector Medical College, Pakistan Jul to Dec 2019. Methodology: A study was carried out on 200 medical students. One hundred undergraduates from all five years and 100 postgraduates/residents from varying specialities were asked to complete DASS 21(depression, anxiety, and stress score 21). Results: Out of 200 students who completed the questionnaire, 116(58%) were depressed. Among the postgraduates, females were more likely to be depressed (p=0.029). 135(67.5%) students suffered from anxiety. Undergraduates were statistically more likely to suffer from anxiety (p=0.011). 101(50.5%) students were stressed. Overall, females were more stressed than male students (0.012). Among postgraduates, females were more likely to be stressed than males (p=0.013). Marital status does not appear to have any effect on depression, anxiety, and stress. 25(12.5%) students had suicidal ideation. Conclusion: Depression, anxiety and stress are present in over half of our medical students, both undergraduates and postgraduates/residents. We need to address this in our hospitals and medical schools by providing easily accessible counselling facilities and psychologists to help them.