Background: One of the most sensitive and stressful, yet important, occupations is that of the nursing population; the study of their physical, mental and psychological health as the basis of primary health care services is of special importance. Of course, attention to their health and assessment of their problems causes to create motivations and effective interventions in maintaining human resources and their job performance. Therefore, the aim of this research was to compare job performance, occupational stress and general health among nurses in the psychiatric and emergency departments. Methods: The statistic population of this research is nurses from the Hospital Milad, Erfanian and Iranian in Tehran. 270 people were selected to distribute the questionnaire. In order to analyze the data, inferential statistics and independent t-test were used. The results were analyzed by SPSS software. Results: Based on testing hypotheses, according to the first hypothesis, the job performance varies among psychiatric department nurses and those of emergency one; according to the second hypothesis, the occupational stress is different between psychiatric department nurses and those of emergency one. Finally, according to the results of the third hypothesis test, the general health is different for psychiatric department nurses and those of emergency one. Conclusion: The results of this research indicate that there are differences between the three structures of occupational stress, job performance and mental health in the two emergency and psychiatric departments of hospitals Milad, Erfanian and Iranian.