Despite of the banking M&A development, all do not allow to increase the performance of theconcerned companies. Indeed, the rate of failure of these operations is hight and since a long time, researchers wonder strongly about the real reasons of these failures. Many factors influencing the performance were moved forward to explain the success or the failure ofa M&A operation ; but these studies, have often based themselves on quantitative esearches methodsnot allowing to detect a single precise and major factor standing out most from all the elements influencing the performance and explaining the merger and acquisition result. Indeed, one exclusively financial vision constitutes a narrow vision of what a banking M&A operation is as its success or its failure also depends on the synergy realization concerning strategic domains, processuel, organizational and cultural of these operations.The mission of our study is to examine the following issue : What determining factor explains the M&A success or failure perceived in the banking sector? Through a qualitative study, constituted and analyzed by the multiples cases method (17 interviews have been conducted), our investigations have tryied to explain how the arbitration between the M&A performance is made, namely a positive or negative result realized, and the performance perceptionwhich have the actors, having lived closely or remotely a M&A opération. Finally , our research shows that the organizational dimension is at the heart of our results having adecisive impact on the M&A result whether it is positive (success) or negative (failure).
