Acquisitions affect not only the acquiring and target firms but also the industry’s competitive landscape, altering rival firms’ performance, as well as their strategic decisions. Thus, rivals are an important acquisition stakeholder. Yet, the literature on rivals’ responses to acquisition announcements and the performance implications of such responses is still incipient, and findings are inconclusive. This chapter offers a systematic review of rival firms’ responses to acquisitions, providing a framework that can help scholars better understand the types of responses and the variables affecting them. Studies are aggregated into the two broad types of responses, namely financial market reactions and strategic responses. The latter are classified into: (1) corporate, operational, and competitive responses, (2) innovation and sustainability, and (3) finance, accounting, and disclosure practices. Directions for future research are also provided.