Although the knowledge base on instructional leadership is quite well developed in Western societies empirical studies have only recently begun to emerge in the developing societies of Asia, Africa and Latin America. The current study was undertaken to fill a gap in leadership research in Iran, where there have been no prior studies of principal instructional leadership (PIL). The current study sought to understand the relationship between principal self-efficacy, instructional leadership, teacher collective efficacy and teacher organizational commitment in Iranian primary schools. Survey data collected from 111 principals and 345 teachers were analyzed using confirmatory factor analysis and structural equation modeling (SEM). The results confirmed the proposed conceptual model affirming the impact of both principal and teacher beliefs (i.e. self-efficacy) on their behaviors and on teacher commitment. More specifically, the SEM results identified robust, positive and statistically significant relationships among the constructs. These findings extend prior research by revealing how leader self-efficacy beliefs and instructional leadership behaviors interact to shape collective teacher efficacy and commitment. This research makes a distinct contribution not only to school leadership research in Iran, but also to the growing body of research on the effects of PIL in non-Western, developing societies.