The scope and nature of conspiracy liability under international criminal law have long provoked controversy among scholars and practitioners alike. The questions whether this notion is a crime, or a form of criminal participation, or both, and what is its relation to the theory of joint criminal enterprise, have been at the core of these debates. The UN ad hoc Tribunals have routinely held that conspiracy is strictly an inchoate crime and is, therefore, fundamentally different from joint criminal enterprise responsibility. This line of reasoning, however, has been challenged by many in the commentariat who continue to argue that the international legislative origins of conspiracy in post-World War II documents and jurisprudence also defined this notion as a mode of liability. Far from being merely theoretical, this debate has been fuelled by a very practical consideration: the argument that since the concept of conspiracy has been shunned in international criminal law ever since the Nuremberg process, the joint criminal enterprise theory should also be repudiated. This article will thoroughly review the Nuremberg-era law on conspiracy in order to evaluate the conflicting interpretations of its legal nature. It will demonstrate that although this notion was originally construed to have a bifurcated function, it was then gradually refined and distinguished already back in those days from the underlying principles of the joint criminal enterprise theory.