This article is an empirical study about the Free Presbyterian Church and its relationship to political change in Northern Ireland. Drawing from interviews conducted with Free Presbyterian clergy between September 2007 and April 2008, it seeks to explain why the Church sought to distance itself from Reverend Dr Ian Paisley's decision to accept power-sharing with Nationalist and Republican opponents in 2007 and why Paisley stepped down as Church moderator after 57 years. The article argues that this occurred for three main reasons. First, accommodation of the political mainstream contradicts the idea of separatism which the Free Presbyterian Church advocates. Second, Paisley's transformation raised serious concerns and doubts about the authenticity of word and truth. And third, many within the Free Presbyterian Church were unable to accept Paisley's decision to share power with those they see as unrepentant criminals and murderers (i.e. Republicans). The analysis takes issue with the suggestion that evangelicals are abandoning their Calvinist convictions as a response to the new political and social landscape in Northern Ireland. It argues that Paisley's decision to lead the Democratic Unionist Party (DUP) into a power-sharing Assembly has led Free Presbyterians to restate their traditional separatist fundamentalist principles and to resist the threat of change.