Many researchers have emphasized the importance of teaching stress management and self-care skills to medical students as they are vulnerable to develop psychological health problems. The researchers designed a 4-hour intervention based on the DEAL model to address these problems. This study aimed to determine outcomes of the DEAL-based intervention on medical students’ stress, anxiety and depression symptoms. Methods: A randomized controlled trial study was conducted on 171 medical students. Their stress, anxiety and depression symptoms were measured by the 21-item Depression Anxiety Stress Scale at five intervals; at 2 weeks before the intervention, and at 1 week, 8 weeks, 16 weeks and 32 weeks after the intervention. The mixed model ANCOVA was applied to determine the effect of the intervention on the participants’ psychological health at five intervals. Results: A total of 153 medical students (intervention = 73 and control = 80) completed this study. Results showed that the intervention group experienced significantly lower stress and depression symptoms than the control group. Although anxiety scores are consistently lower in the intervention group, no significant differences between groups were found. Conclusion: These results support the favourable outcomes of the intervention on psychological health of medical students. It is a promising intervention to be considered by medical schools as it consumes minimal amount of time, money, training and man power as well can be implemented easily.