This dissertation focuses on the phenomenon of Digital Security Governance (DSG), highlighting how “digital security” has emerged as an ongoing strategic concern for contemporary organizations. The objective of this dissertation is to provide theoretical and empirical understanding of the currently under-researched aspects of the DSG phenomenon, i.e., what goes on in the implementation of DSG, how DSG can learn from related fields, and how DSG can be governed to become effective in countering the increasing occurrence of cyber failures. The research aggregated in this dissertation advances knowledge and understanding regarding DSG in multiple ways. The literature review in Chapter 2 reveals a fundamental call for a need for change "from the basement to the boardroom." In an ever-increasing digital and technology-driven world, DSG is a strategic concern that affects the long-term success of organizations at the organizational-wide level. Chapters 3 and 4 provide a thorough understanding of "why" organizations fail to establish successful security governance. Chapters 3-5 together provide direction for answering the research question on "how" organizations can effectively implement and govern security governance approaches in today's ever-changing digital landscapes.