Despite growing attention to the role of social context in determining political participation, the effect of the structure of social networks remains little examined. This article introduces a model of interdependent decision making within social networks, in which individuals have heterogeneous motivations to participate, and networks are defined via a qualitative typology mirroring common empirical contexts. The analysis finds that some metrics for networks' influence—size, the prevalence of weak ties, the presence of elites—have a more complex interaction with network structure and individual motivations than has been previously acknowledged. For example, in some contexts additional network ties decrease participation. This presents the potential for selection bias in empirical studies. The model offers a fuller characterization of the role of network structure and predicts expected levels of participation across network types and distributions of motivations as a function of network size, weak and strong ties, and elite influence.