The main aim of this article is to introduce the concept of mental health decolonization through an examination of the beginnings of this process during the Cold War. For this reason, the discussion of the appearance of global and local projects in transcultural psychiatry is introduced. As the object of our main documentary analysis, we chose the final report of the World Health Organization's transcultural project conducted between 1965 and 1973 in the Global South and Global North, entitled International Pilot Study on Schizophrenia (WHO, IPSS 1973). Our aim is to identify, through the analysis of this WHO global cross-cultural project, how mental health and culture were treated as a medico-political project aimed at creating a common language for psychiatry through a universalist epistemology. The WHO is tied to the social problems of the postwar period, seeking in the epistemology of universalism a confirmation of the fact that we are all equal, and also an opportunity to avoid future conflicts between individual nations. World peace, world citizenship and universalism are important medico-political agendas of the IPSS and especially the WHO. In terms of structure of the psyche, the decolonial approach holds that all humans are the same, respectively the same level. Although the universality of schizophrenia has played an important role as a critique of colonial psychiatry, IPSS takes a very risky and limited path. The problem is that we are not all the same. Subjectivity is at stake, diversity and different cultural and social aspects that need to be taken into account. In this sense, the attempt to create a common and universal language for schizophrenia raises questions about some postcolonial and transcultural approaches.