Dysregulation of Wnt signalling, a hallmark of which is the stabilization of the transcriptional co-activator β catenin, can lead to several types of cancer, including prostate cancer. Activation of the Wnt/β catenin pathway has effects on prostate cell proliferation, differentiation and the epithelial–mesenchymal transition. In this Review, the authors discuss how the pathway is activated and consider the possible therapeutic application of drugs that target Wnt/β catenin signalling.