This study conceptually and empirically explores how project complexity and bonding forms of social capital influence performance outcomes in network organizations. Specifically, we focus on how bonding social capital within network organizations—measured as frequency of collaboration and degree of network coupling—can influence project performance outcomes both (a) directly by facilitating cooperative interaction and (b) contingently by mitigating the transaction costs associated with the management of complex projects. Using longitudinal data on contracted construction jobs to test our hypotheses, we find that project complexity is negatively related to project performance and bonding social capital has both direct and moderating effects. Contrary to expectations, however, we find that the different types of bonding social capital affect project performance uniquely and not always in an improved direction. Our findings suggest a more multifarious relationship than previous social capital research might imply.