Buying domestic products has become increasingly important in many countries. As a form of social influence, social norms affect people’s domestic purchasing intentions and behavior. The current study aims to examine the mechanisms by which social norms influence domestic purchasing intentions through the lens of consumer ethnocentrism and domestic product judgments. The data were collected through an online survey in China, and a total of 346 valid responses were obtained. The results indicate that social norms influence domestic purchasing intention through four paths, namely, direct path, motivational path, cognitive path, and motivational–cognitive path. Consumer ethnocentrism and domestic product judgments, serving as the motivational and cognitive factors, respectively, play mediating and serial mediating roles in the relationship between social norms and domestic purchasing intention. In addition, consumer ethnocentrism has two dimensions, namely, pro-domestic and anti-foreign consumer ethnocentrism, and only the former plays a significant role in the model. The current study has theoretical contributions to research on domestic purchasing intention and practical implications for interventions in domestic purchasing behavior. Future studies are encouraged to conduct experiments, distinguish between different types of social norms, measure purchasing behavior, and verify the relationships in other countries.