The purpose of this study is to examine how organizational justice and diversity management influence organizational performance in the public sector. In contrast to the dominating view that organizational factors lead to increased levels of organizational performance, this article includes public service motivation and extrinsic motivation for observing the mediating role of the dynamics of employees’ motivation on organizational performance. This paper develops a hypothesis proposing that motivation mediates the relationship between organizational justice and perceived performance. Data come from the 2010 U.S. Merit Systems Protection Board survey. Principal component factor analysis and structural equation modeling are used to estimate the effects of public service motivation and extrinsic motivation on the relationship between organizational justice, diversity management, and organizational performance. Public service motivation is a positive mediator in the relationship between organizational justice and diversity management, and organizational performance, while extrinsic motivation is a negative mediator. Total effects of the structural equation modeling are still larger than direct effects. These findings suggest that public service motivation and extrinsic motivation, associated with fairness in public organization setting, increase organizational performance.