Aim: The aim of this study was to determine the effect of modern public management on organizational citizenship behavior according to the mediating role of organizational trust. Methods: The research method was applied in terms of purpose and descriptive - survey in terms of the data collection method. The statistical population of the study included all employees of Qeshm Trade - Industrial Free Zone that of them; 270 people were selected using Cochran's formula and stratified random sampling method. The data were collected with the Moghimi Organizational Citizenship Behavior Questionnaire (2011), The Organizational Trust Inventory (2003), and the Questionnaire of Modern Public Management. Data were analyzed by mean, standard deviation, percentage, frequency through SPSS software, and statistical inference of data by Structural equation modeling with Lisrel software. The technical characteristics of the questionnaires including reliability, convergent validity, and divergent validity were investigated. Path coefficient and significance of coefficient software were used to investigate the research study. Results: The findings showed that the degree of appropriateness of the proposed model was appropriate according to the research components; also, modern public management had an effect on organizational citizenship behavior with the mediating role of organizational trust in 0. 82, modern public management had an effect on organizational citizenship in 0. 61, modern public management had an effect on organizational trust in 0. 48 and organizational trust on organizational citizenship behavior in 0. 45. Conclusion: Therefore, modern public management affects organizational citizenship behavior according to the mediating role of organizational trust