The aim of this study was to investigate the effect of perceived organizational support on organizational commitment through mental happiness in the staff of the Imam Khomeini Relief Committee in Shiraz and using a descriptive correlational research method. The statistical population of this study is all employees of the Shiraz City Relief Committee, which in March 2016 was 267 people. The tool for collecting field information in this research is a questionnaire. The Mental Happiness Questionnaire consists of a combination of Life Satisfaction, Positive and Negative Emotion and Job Nature Questionnaire. The analysis of this study was performed using SPSS23 and Amos23 statistical software at two levels of descriptive statistics and inferential statistics. The research findings confirm the effect of perceived organizational support on organizational commitment through mental happiness. Also, the direct effect of perceived organizational support on organizational commitment and its dimensions, the effect of perceived organizational support on mental happiness and its dimensions and the effect of mental happiness on organizational commitment and its dimensions have been confirmed. The results of demographic hypotheses showed that there is no significant difference between the level of organizational commitment, perceived organizational support and employees' sense of mental well-being with respect to the gender variable; But there was a significant difference between the respondents' opinions about the feeling of mental happiness according to the variable of education level. There is also a significant difference between the level of organizational commitment and perceived organizational support with respect to the organizational category variable.