Abstarct: The present study aims to investigate the impact of sustainable human resource management on organizational citizenship behavior for the environment and proactive behavior, with the mediating role of spirituality in the workplace. This research is applied in terms of purpose and descxriptive survey correlational in terms of data collection method. The statistical population consisted of approximately 4,600 employees from the human resources, production, environment, maintenance, research and development, and process improvement units at Iran Khodro Company. baxsed on Cochran's formula, the sample size was determined to be 354 individuals, and stratified random sampling proportional to the size of each organizational unit was employed. To compensate for unreturned questionnaires, 25% more than the minimum sample size were distributed. Data were collected using standardized questionnaires with a five point Likert scale, whose validity was confirmed through content and construct validity, and whose reliability was verified by calculating Cronbach's alpha coefficient. The collected data were analyzed using statistical software and structural equation modeling with the partial least squares approach. The findings showed that all seven proposed hypotheses were confirmed. In other words, sustainable human resource management has a positive and significant effect on employees' environmental citizenship behavior and proactive behavior, both directly and indirectly through the mediation of spirituality in the workplace. These findings reveal an important reality: when organizations implement sustainable approaches in human resource management and simultaneously provide a context of meaning and purpose in the workplace, employees are not only encouraged to perform extra role behaviors for environmental protection, but also gain the courage and confidence to present innovative and out of the box ideas. The significance of this finding lies in showing that spirituality in the workplace is the missing lixnk that can connect sustainable HR policies to employees' innovative and pro environmental behaviors.