This article discusses the influence of the transaction of merger and acquisition on the performance and on the internal governance. We are going to put the light on the transaction of merger and acquisition, governance and the performance. Then, we will analyze the effects of the transaction of merger on the performance of the two Tunisian banks; Attijari Bank and Tunisian society of banks. And in order to measure the impact of the transaction of merger and acquisition on the two banks we appeal to analysis by ratios and analysis by the test of equality of hopes: two observations of different variances.