In this article, we draw on cultural cisgenderism to analyse the sporting experiences of trans men in Iran. Utilising semi-structured interviews with twelve trans men in different stages of transition, we consider their experiences of women's sport environments, the extent to which cisnormativity is embedded into the culture, and whether their gender identities are accepted. We found that essentialist understandings of sex and gender are evident in sport environments, with gender presentation policed by others, and expectations this should align with ascribed biological sex. While some interviewees’ masculine expressions were valued, others were considered ‘too masculine’ to be eligible to participate in women's sport spaces; this led to restrictions around appearance and clothing, alongside instances of compulsory hormone testing. Finally, for those who were ‘out’ about their gender identity, this often led to hostility from others, including coaches, teammates, and spectators. Overall, this paper provides a critical understanding of trans inclusion in sport spaces in Iran. However, the findings may be useful for anyone working to make sport more accessible, regardless of geographical location.