In the literature on morality issues, the most famous typology distinguishes countries from the “religious” and “secular” worlds, based on the presence or absence of partisan religious cleavages. Portugal belongs to the former world, yet in 2018, the Portuguese Parliament passed a law on the self-determination of gender identity. This article asks how such an outcome was possible, focusing on the role of political parties and civil society actors within advocacy coalitions. Our analysis reveals that, in addition to the role played by civil society actors, the “change coalition” won the dispute because it assembled a majority of votes in the parliament from left-wing progressive political parties. Moreover, actors from the “change coalition” developed a clear strategy of articulation before and during the debate. In contrast, the “blocking coalition,” composed of right-wing political parties and a few health-related actors, failed to define a coherent advocacy strategy.