As the mission-driven organizations, nonprofit organizations rely on their employees to deliver the services that nonprofit stakeholders expect.The understanding of the issue what motivates people to serve in nonprofit sector rather than profit or public sector should precede the competitive strategies which nonprofit organizations adopt to enlist the desirable employees. The nonprofit sector has its own genealogy of employees and their service motivations are distinct from those for-profit and public sectors. Altruism is only one side of the nonprofit coin. Unlike the conventional frameworks of motivation theory such as the dichotomy between extrinsic and intrinsic motivators, the service motivation matrix categorizes individual motivation into four sub-types based on the service constraint level (Active versus Passive) and the service focus or orientation(Altruism versus Egoism). This matrix will increase our understanding of the underlying motivation for the explicit service choices of employees in the nonprofit sector and serve as a basis for future empirical analysis.