This book unifies and draws a connection to different concepts of organizational behavior, decision-making theories, psychology and strategy research. Furthermore, it focuses on the theoretical backgrounds of managerial decision-making, different personality concepts and their impact on strategic decisions. Since strategic decisions are made by individuals, it is worth analyzing to what extent personality phenomena such as hubris influence the choice between acquisitions and alliances. In fact, both governance modes are a necessary prerequisite for companies to remain healthy, gain competitive advantages and hence, become world leaders. First, this book provides a literature review of the current research status on governance modes, particularly laying an emphasis on acquisitions and alliances. Moreover, it is explored what hubris actually means, which different facets are underlying and how it is different from other related concepts, such as narcissism, overconfidence, and core self-evaluations. Subsequently, studies having dealt with the concept of hubris in general, hubris in investment decisions and hubris in governance mode decisions in particular are analyzed. Numerous of these studies on strategic and investment decision making have found managers infected with hubris to regularly overpay for acquisitions but none has yet analyzed whether hubristic decision-makers also prefer acquisitions over alliances and which decision making criteria they consider when making such governance choices. Therefore, data from students and executives are collected with the help of a policy-capturing approach - a method used to find out more about individuals’ underlying judgment and information-processing strategies. Moreover, measures to assess personality phenomena are adapted and developed. Thus, this study adds to the growing body of literature on acquisitions vs. alliances by including hitherto neglected personality variables and hence providing a richer explanation for governance decisions. Analyses are conducted with hierarchical linear modeling and logistic regression. This book closes by discussing important results, limitations and implications for both research and management.