Developing and continuing with a sustainable business requires employees who generate positive feelings and possess motivation towards the organization, where it enables the organization to achieve a competitive edge. In achieving that competitive edge, the role of the leader is significant as it influences the behavior of the employees. The purpose of this study is to investigate how transformational leadership of a leader and psychological empowerment of subordinates are related to voluntary commitment of the employees apart from defined roles and responsibilities. Here, the voluntary commitment of employees is identified as organizational citizenship behavior manifested by employees. The data were collected from 130 employees of an apparel sector manufacturing organization in Sri Lanka. They responded about their superior’s leadership, their own empowerment, and whether they go beyond the basic requirements of the job. Data were collected through a self-administered anonymous questionnaire which comprised of standard measures for each variable. Accordingly OCB was measured by the measure developed by Podsakoff, MacKenzie, Moorman, and Fetter (1990), transformational leadership was measured by the shorter version presented by Hinkin and Tracey (1999) of the transformational leadership measure developed by Bass and Avolio (1990).  Psychological empowerment was measured by the 12 item original measure developed by Spreitzer (1995) covering four dimensions. The positive effect of transformational leadership on organizational citizenship behavior of employees was significant and the mediating effect of psychological empowerment on the relationship between transformational leadership and organizational citizenship behavior of employees was also found significant, with partial mediation being supported. The theoretical development of this paper will contribute towards understanding the effects of transformational leadership and psychological empowerment on OCB and thereby contributes to the knowledge related to those concepts. This study can help in developing practices to improve the psychological empowerment of employees and also guides leaders to focus on enhancing OCB through bringing a change in the style of leadership, to the organization.