Populism often emerges with a strong homo- and transphobic orientation. This is the result of an alliance between populism and conservative religion. Populist movements have incentives to reach out to religious voters and vice versa. We argue that the alliance between populism and religion is both a marriage of convenience and inconvenience. Populists can offer attacks on pluralism and liberal social policies (e.g., pro-LGBTQ laws), which conservative religious groups often welcome. In return, religious groups can deliver loyal acolytes across classes, which populists also welcome. Religion enables populist movements to expand their constituency beyond their base of economically anxious and nationalist voters. That said, this alliance works best only where the conservative religious electorate is growing (or, at least, not declining). Even then, this union can still incite internal frictions within populist coalitions. These frictions tend to be more salient within left-wing populist coalitions than right-wing ones. This explains why the populist-religion nexus is more resilient among right-wing populist movements, as cases from the Americas and Europe illustrate.