Abstract : This chapter aims to first understand the evolution of Protestant churches’ positions on same-sex marriage and to shed light on the convergence of views, on the one hand, between Catholic and Protestant churches and, on the other hand, between the different Protestant streams. Then I will question the relevance of a strict distinction between Lutheran-Reformed Protestants and Evangelicals as a sociological key to analysing the Protestant attitudes towards same-sex marriage. This example will show why intra-Protestant “theological” criteria don’t bring a sufficient explanation for a sociological understanding. The risk here consists in reproducing theological criteria as they are elaborated in the Protestant field, without examining the social and institutional stakes linked with these distinctions. Finally, a controversy between two major sociologists of religion during the debate on same-sex marriage will show the tensions generated by an incomplete process of secularisation of the sociology of religion in France.