In this research I surface the epistemological assumptions underpinning thinking on the apparent high numbers of people with mental illness in Africa not receiving care, known as the ‘treatment gap’. I thus prise open the ‘black box’ of this knowledge, scrutinising its underlying meaning codes and capillaries of power. I explore knowledge produced on the ‘treatment gap’ at three different sites: 1) Mental health research in Africa published over the last decade; 2) National mental health policies of 14 African countries; 3) Narratives of 28 psychiatrists all working in public mental health care provision in South Africa, Uganda, Ethiopia or Nigeria. For my analysis I develop a theoretical toolbox which draws on concepts from two broad and multidisciplinary fields, namely Science and Technology Studies (STS) and Postcolonial Studies. What emerged was that knowledge on the ‘gap’ in mental health care is deeply inserted within the episteme of European Colonial Modernity, and thus saturated with Eurocentric tendencies. In particular, two paradigms are playing a fundamental role, those of evidence-based science (including biomedicine) and human rights. I destabilise the inevitability of these paradigms by putting them in historical perspective, and shedding light on the many questionable certainties and binary oppositions upon which they are based. I show how they have become the gatekeepers of knowledge, ultimately occluding ‘other’ ways of knowing which are based upon alternative epistemological codes. The somewhat singular voice of scholarly authority was, however, at times softened by certain quieter and more marginalised voices. These suggested avenues out of which more decolonised, ‘Africa-focused’ models of scholarship might potentially grow. To sum up, I surface particular tensions and hold them up to the light, with the hope of disturbing certain intellectual reflexes and creating a space for potential alternatives. Ultimately, this might help foster different sorts of conversations on the ‘treatment gap’ from those created by current seats of power.