This study focuses on knowledge management role in Mergers & Acquisitions (M&A). With high proportion of M&A failure, it is important to define possible ways to increase M&A success rates. Knowledge acquisition and management is the important part of M&A initiative, as it forms the foundation for M&A decisions. But with M&A high complexity, uncertainty and ambiguity, effectively organized knowledge management of M&A can become a challenge. In this article authors review current research on knowledge management in general and M&A specific knowledge management, identify the levels of M&A knowledge hierarchy, namely – individual M&A initiative scope, M&A initiatives in scope of one company, M&A initiatives in scope of the same industry. For each level success factors and obstacles for the effective knowledge management are defined. As a result, a proposal for M&A knowledge management high level framework is presented, accumulating all knowledge management levels, and defining the knowle dge structure and flow between them.