The essence of mergers and acquisitions (M&A) process is the integration of two or more organizations into a new organization, and an organization is a cooperative system of human activities. Therefore, cooperation is a key issue in post-M&A human resource integration. Based on social identity theory, this study explores the influence mechanism of acquired employees' self-continuity on cooperative behavior in the context of M&A through questionnaire survey data of 196 acquired employees. The results show that acquired employees' self-continuity has a significant negative effect on cooperative behavior in the context of M&A. Anxiety plays a mediating role in the relationship between self-continuity and cooperative behavior. Perceived cultural distance not only moderates the relationship between self-continuity and anxiety, it also moderates the mediating effect of anxiety, such that anxiety is stronger when perceived cultural distance is higher than when it is lower. This study enriches the research of post-M&A human resource integration, explores the negative effect of self-continuity, and provides beneficial implications for promoting employees' cooperation in the context of M&A.