This research analyses the effects of the knowledge overlap between acquirer and target firms on the performance of technological mergers and acquisitions (M&As). Extending previous research that has focused on the quantitative characteristics of knowledge, this research introduces a framework capturing the effects of both the quantity and quality of knowledge in overlapped and nonoverlapped parts of the knowledge base on subsequent innovation performance. Analyzing a data set of 192 technological M&As of 162 high-technology firms from 2001 to 2009, the results show that a high quality of overlapped knowledge has a positive effect on subsequent innovation performance, while the effect is negative for nonoverlapped knowledge quality. In addition, this research investigates the influence of the knowledge quantity on subsequent innovation performance. The implication of this research is that the knowledge overlap in technological M&As is essential for acquiring high-quality knowledge from the target firm and for improving innovation performance.