Mergers are one of the most important business activities conducted by companies. Nowadays, mergers are an established instrument of corporate development in order to increase long-term shareholder value. Simultaneously, mergers are one of the most risky strategic decisions that can easily lead to failure. The most prominent example in this context is the merger of Daimler-Benz AG and Chrysler Corporation, which failed due to the strategic mismatch and operational problems with a sale of Chrysler in 2007. Based on the high merger failure rate, the theoretical analysis in this paper focuses particularly on the motives and explanations for mergers. According to Efficiency Theory, companies can complement their specific Strengths– Weaknesses Profile and thus, benefit from synergy effects. The Efficiency Theory is based on the idea that the result of bundling activities delivers more value than working separately. In addition, strategically motivated mergers exist, which are aimed at closing resource gaps through the merger with a target company. But the most important question is: how do successful mergers differ from those that fail? The risk of failed mergers can often be explained by misjudgment of the target company. Accordingly, the success of mergers depends on appropriate merger strategy, which analyzes strategic success factors and matches the business strategy of acquirer and target companies.