Taiwan has experienced a number of party splits and attempted mergers since democratization. These have played a critical role in the development of the country's party system. While a number of studies have looked at the emergence of Taiwan's splinter parties, party mergers have not received academic attention. This study aims to systematically examine the process of party mergers and takeovers. We examine four cases of attempted mergers and takeovers. In each case, we focus the analysis around three core questions: (1) How should we best classify the actual outcomes? (2) How we can best explain the variation in outcomes? (3) How can we assess the success of merger/takeover attempts? Unlike earlier studies, we examine a variety of merger outcomes rather than just successful cases. In addition to mergers, we propose the terms negotiated takeovers and hostile takeovers. Our classification scheme is based on relative party power and the inter-party relationship. To explain the variation in outcome, we applied a framework stressing the interplay of contextual, inter-party and inner-party factors. We found key contextual variables were electoral results, relative party sizes and the electoral system. The most important inter-party variables were ideological proximity and inter-party trust following successful cooperation. Lastly, the inner-party balance of power was also critical, particularly, the strength of leaders with favorable attitudes toward the merger project. We assess the success and failure of merger/takeover attempts with reference to election results, post-merger party unity and whether the post-takeover relationship was cooperative.