Although intergroup conflict caused by demographic differences in organizations disrupts social interactions between employees, little empirical research has been conducted to understand how to effectively manage demographic diversity in the public workforces. By combining two theories of diversity and inclusion, this article explores the independent and joint effects of three dimensions of demographic diversity (gender, race, and age) and a diversity climate on organizational social capital in the U.S. federal government. Statistical analysis shows a negative relationship between age diversity and organizational social capital and a contrasting positive relationship between a diversity climate and social capital. More important, the diversity climate as a key moderator conditions the impact of racial diversity and age diversity on social capital. The findings suggest the importance of a supportive diversity climate in improving the quality of social relationships within demographically diverse organizations.