Maritime Domain Awareness (MDA) is often heralded as a sort of silver bullet, allowing resources to be employed effectively across maritime security agencies, but also different jurisdictions. MDA is believed to be a core enabler for international maritime security cooperation and is seen as one of the most important tools in addressing maritime security threats, such as piracy, illegal fishery, smuggling or maritime terrorism. This chapter traces the origins and evolution of MDA. I then provide a short history of developing regional MDA in the form of inter-governmental information sharing centres. My reconstruction documents the gradual evolution of MDA structures leading up to an emerging transnational network set up over the past two decades. The succeeding sections then ask a range of questions towards MDA seeking theoretical and empirical evidence for and against its core premises. What kind of evidence exists so far, which would justify the claims that MDA is a core enabler for transnational cooperation, increase effectivity and addresses the capacity gap? What kind of theoretical premises might support such conclusions?