Transgender people face high rates of discrimination and health problems yet supportive policy measures are often opposed, especially by religious organisations adhering to cis-normative theologies. Scholars exploring the links between religion and transgender issues have examined a number of themes, but the way religious actors discursively frame transgender issues remains under-researched. This article contributes to work in this area by using the concept of political opportunity structures to examine the discourse of religious groups on the 2022 Scottish Gender Recognition Reform Bill. The study shows that arguments were typically framed in secular terms, drawing on the epistemic authority of science and a language of individual rights. Supporting groups used arguments designed to highlight the difficulties that transgender people face. Oppositional groups used themes based on biological essentialism, concern for the well-being of trans people, the risks to cisgendered women and warnings about the negative impact on society and religious freedoms.