This article applies social exchange theory to investigate the relationships between work opportunities and organizational commitment in four United Nations agencies. It demonstrates that international civil servants who are satisfied with altruistic, social, and extrinsic work opportunities are more likely to declare high levels of organizational commitment. Furthermore, the perceived organizational support mediates these relationships. The empirical findings highlight the importance of considering the specificity of organizational features in explaining international civil servants' attitudes and behaviors. Their preferences for altruistic, social, and extrinsic work opportunities are not similar to the motivational orientations and rewards valued by public- or private-sector employees, thus confirming the hybrid characteristics of international organizations. Drawing on these original results, this research also identifies some practical implications for human resources management in international organizations.