High quality leadership and support from the organization are two well-established factors that influence an individual’s commitment to their organization. However, very little is known about the processes through which these variables influence commitment. This empirical study drew on theory and research to propose person– organization (P–O) fit as a mediating variable to explain these relationships. A sample of 6,503 personnel in the Canadian Armed Forces provided responses to a personnel survey. Results indicated that P–O fit fully mediated the relationship between leadership satisfaction and organizational commitment and partially mediated the relationship between perceived organizational support and organizational commitment. These results contribute to the extant literature and theory by testing these relationships in a military context and by demonstrating the importance of P–O fit as a mediator of leadership, support, and organizational commitment. The results and their implications are discussed with particular emphasis on their importance in a military environment.