Customers are important stakeholders for any company; yet, they seem not to be widely discussed in merger and acquisition research. This chapter synthesizes the current body of research on customers in mergers and acquisitions through presenting a systematic literature review. The chapter is based on a systematic literature review resulting from a search in EBSCO Host for any research item that refers to “customer” and “consolidation or merger of corporation.” All articles were coded to specify how customers are described, with a focus on whether customers are expected to affect and/or be affected by the merger or acquisition. Articles were compared with regard to their year of issue and research disciplines of publishing journals. The review indicates how customers continue to be discussed only to limited extent. The customer roles array from them as an acquirable customer base to customers as actors, whose activities become the very reason to merge or acquire. Literature also refers to them as victims and affected by the merger or acquisition, and reacting parties. In addition to the description of welfare transfer from consumers to acquirers in law and economics studies, the different ways of referring to customers extend beyond specific research disciplines. The literature review indicates more multifaceted ways of describing customers in recent research. No systematic literature review on customers in merger and acquisition literature has previously been conducted. The comparison of research disciplines, years of issue, and customer roles provides new insights into developments in the merger and acquisition field of research.