The managers cannot be expected to have the same anxiety while using the money of the others. This is the issu what ‘corporate governance’ deals with. This book aims at providing information about the effects of corporate governance on the performance of the firms during the financial crisis. Firstly the reasons of the emergence of the corporate governance is focused on, then generally accepted principles of corporate governance were explained; Anglo-Saxon and Continental approaches were focused on. Then chronologic, legal and civil aspects of the corporate governance applications in Turkey are emphasized.In the Empiric study, 167 manufacturing firms listed in Istanbul Stock Exchange were analyzed. The performance (ROA) of these firms in 2008 crisis was examined through SPSS 17.0 program. The relationship of the performance, detected with regression analyses, with corporate governance was determined.