Since the tragedy of September 11, 2001 (9/11) there have been a growing awareness and recognition of the expanding threat presented by the transmutation and convergence of international organized crime and terrorist groups. There is a semantic debate on whether these organizations are “converging” or “transforming.” Regardless, this worrisome development is complicated and progressively difficult to combat and calls for law enforcement, intelligence and military interventions. While the United States and other countries have been dealing with the post-9/11 world of persistent problems like Iraq, Afghanistan, al Qaeda, “Islamic State in Iraq and Syria” (ISIS), Syria, and more, the links between organized crime and terrorism could prolong these challenges and generate further disruptions and menace to global security and development. There are strong operational needs and requirements that bring organized crime and terrorists together for collaboration and even seamless transitions within the same general operation. However, there are substantial hurdles that make a total teamwork between the two groups not so easily achievable. For example, organized crime normally avoids the publicity and the indiscriminate killings often used by terrorists. However, it is clear that the merging of international organized crime and terrorist groups is growing and presents unique challenges and opportunities. This paper examines this ongoing transmutation, convergence and cooperation between transnational organized crime and terrorism, and offers examples and recommendations on how to prevent it and defeat it.