This study investigates how informal institutions may have a crucial impact on the social processes of network formation and consequently the interorganizational network structure. We test our hypotheses by exploring how clan culture influences firms’ alliance network structure. Using data from Chinese A-share listed firms from 2010 to 2021, our findings indicate that the focal firm’s local clan culture in the region increases its alliance network closure. Furthermore, we further examine the moderating role played by the executive characteristics in the TMTs and discover that the number of female executives in the TMTs reduces the impact of clan culture on the alliance network closure, whereas executives’ oversea experiences only have a marginal moderating effect. These findings deepen our understanding of the connections between informal institutions and interorganizational network structure. Moreover, by discovering the female executives’ distinct effect on firms deriving from their perceptions of patriarchal culture, we also contribute to female leadership research.