There is a growing field of research dedicated to online incel communities, gathering men identifying as involuntary celibates or ‘incels’. A distinctive aspect of the incelosphere is the elaborate ‘theoretical framework’ communicated in the forums, portraying incel men as voiceless losers at a (hetero)sexual market ruled by women and biologically superior men. While the content of this incel worldview is relatively well-studied, a notable gap exists in the examination of the way knowledge production taking place within these communities is epistemologically legitimized. This article aims to fill this void by scrutinizing the epistemic logics and practices used by members at incel forums to validate their knowledge production on gender relations. By shedding light on how incels mobilize science as well as counter-hegemonic forms of knowledge production to legitimize their knowledge claims, the article offers a nuanced understanding of the intricate relation between the knowledge production of movements and counter-movements. This exploration can, we believe, form a basis for challenging and contesting claims made by incels.