This research presents a model of organizational citizenship behaviors (OCBs) mediated by social network ties using gender as a moderator. In the proposed model, OCBs are influenced indirectly by the need for power-prestige, outcome interdependence, and person-organization fit through the mediation of instrumental ties and expressive ties, which are considered social network ties. Gender moderates several paths in the model. The moderating effects of gender are simultaneously examined using data collected in Taiwan. Test results show that the influence of the need for power-prestige on expressive ties is stronger for women than for men, and the influence of the need for power-prestige on instrumental ties is stronger for men than for women. Moreover, the influence of outcome interdependence on instrumental ties is stronger for men than for women. Finally, detailed findings and their implications are discussed.