Taiwan’s legalization of same-sex marriage in 2019 made it the first nation in Asia to grant marital rights to gay and lesbian couples. In the years leading up to legalization, the Marriage Equality Coalition Taiwan (pro-same-sex marriage) and the Coalition for the Happiness of Our Next Generation (anti-same-sex marriage) mobilized large-scale social movements on social media between 2016 and 2017 to influence the legislative process. The network structure and affordances of digital platforms have facilitated communication and mobilization for social movements. However, new technology alone does not guarantee participation, and cultural aspects of mobilization on digital platforms are an important area of study. This paper examines the framing strategies these two organizations used on Facebook pages and the political and cultural contexts that facilitated or constrained frame alignment. A mixed-method framing analysis combining quantitative and qualitative methods of their Facebook posts revealed that the supporting group framed same-sex marriage as an issue of human rights and as a democratic development linked to Taiwan’s goal of national independence, whereas the opposing group framed it as a destruction of traditional culture concerning family values and social order. Our analysis identified the distinct features of framing strategy in Taiwan’s marriage equality movement and countermovement, including the appeal to nationalism and the downplaying of religion, that were affected by Taiwan’s specific political and cultural contexts.