Abstract Strategic voting occurs when voters make vote choices using their ex ante expectations about the results of an election in addition to their sincere candidate preferences. While there is ample theoretical reason to believe strategic voting should occur under certain electoral conditions and institutional arrangements, the evidence for it in the literature has been mixed. I theorise that the polarisation of the two main British political parties and the highly publicised predictions of defeat for Britain’s primary national third party, the Liberal Democrats, make the 2015 UK election an ideal case for studying strategic voting. I adapt established methods of identifying strategic voting to this election and find evidence that Liberal Democrat voters in the UK voted strategically for Labour and Conservative candidates to maximise their odds of affecting the electoral outcome in their constituency.