In order to maintain the existence of companies in a competitive environment caused by globalization and developing technology,to continue their activities more strongly by creating synergies, the importance of mergers and acquisitions both nationally and internationally keeps on increasing. In this master thesis, the historical development, the process of mergers and acquisitions, and the reasons that led companies to successfailure were emphasized and with a case study, performanceuation study was carried out by analyzing the company's financial statements before and after the merger on the factors affecting merger and takeover performance.