Introduction: Contemporary studies of organizational citizenship behavior (OCB) are recognized as essential for modern organizations. These studies indicate that organizations with more emphasis on the OCB are healthier and more successful. The results also show that employees, who act beyond their job duties and exert OCB, belong to high productivity workgroup and enterprise with excellent quality in comparison to employees with low level of OCB. Therefore, the investigation of antecedents of organizational citizenship behavior can help the organizations to improve and reinforce it. Thus, the present study aimed at investigating the mediating effect of organizational culture on the relationship between transformational leadership and OCB. Method: A descriptive correlation research method was employed in this study. A total of 160 experts at Shiraz University were selected as the research sample through simple random sampling method using Cochran’s formula. Moreover, the study employed three instruments, namely Bass and Avolio’s transformational leadership questionnaire, Podsakoff’s et al.’s (1990) organizational citizenship behavior scale, and Denison organizational culture survey (2006). It is noted that the reliability of all the scales was obtained through Cronbach’s alpha coefficient. To analyze the research data, Pearson coefficient and structural equation modeling were used through SPSS 22 and Lisrel 8.8 software. Results: The results indicated that of dimensions of transformational leadership, inspirational motivation (β=0.33), and individualized consideration (β=-0.23) directly influenced OCB. Moreover, these two dimensions indirectly influenced OCB through organizational culture (dimension of involvement). The direct and indirect (β=0.16) effect of inspirational motivation on OCB was positive whereas individualized consideration directly had a negative and indirectly (β=0.14) a positive effect on OCB. Two other dimensions of transformational leadership (intellectual stimulation and idealized influence) influenced OCB only indirectly and through organizational culture (dimension of involvement). It was also found that among various dimensions of organizational culture only involvement (β=0.35) positively and significantly influenced OCB. Conclusion: When transformational leaders provide close, intimate, supportive and developed relationships, workers tend to more exhibit high levels of OCB and are motivated to fulfill tasks beyond their formal roles to benefit the organization. We can conclude that employees who act beyond their job duties and show OCB have a high productivity with excellent quality in comparison to employees with low level of OCB. Also, organizations with more emphasis on the OCB are healthier and more successful.
