Research on organizational demographics has been an important development in organizational studies. Building on the latest literature in this stream of research, the present investigation hypothesized the main effects of relational diversity (i.e., demographic differences) at the individual level and compositional diversity (i.e., demographic heterogeneity) at the team level on employees' organizational citizenship behaviors and trust in coworkers. Furthermore, drawing on the perspective of social information processing and the concept of strong-weak situation, we proposed the moderating role of demographic heterogeneity in the relationships between demographic differences and the outcome variables. Using survey data from 488 employees in 64 administration departments in small and medium companies, the main effects and the moderating effects of interest were partially supported. Based on the findings, practical implications and suggestions for future research in organizational demographics arc addressed.