This article offers a critique of the Nuremberg-inspired paradigm of international criminal justice, which focuses on high-profile, top-down approaches to post-conflict accountability. To this end, it appraises the work of the United Nations War Crimes Commission as a “path not taken.” We discuss the very different approach to supporting post-conflict justice adopted by the UNWCC—from its original support base beyond the major geopolitical powers, to the impact of its more deliberative system, to the role of the UNWCC as a hub in which new practices of international law were developed. Such an approach had its achievements: the UNWCC assisted in prosecuting significantly more cases than the International Military Tribunals at Nuremberg and Tokyo, as well as the subsequent Nuremberg Military Tribunals, and its structure lent itself to effective use of national expertise and resources. It also had weaknesses and limitations. The Commission was unable to resist great power politics, which eventually led to its demise. We then discuss the implications of such a model for modern-day international criminal justice. While many of the advances made by the UNWCC have echoes in modern-day processes of “convergent evolution,” there is much still to learn from examining this period of institutional innovation. Recent efforts to institute “positive complementarity” and more cooperative, facilitatory, and horizontal criminal justice institutions could benefit from exploring the UNWCC model. While it remains strictly within liberal approaches to international criminal justice, we argue that the UNWCC represents a clear alternative to the “Nuremberg model” and contemporary approaches to international criminal law, including the work of the International Criminal Court.