Wnt/β-catenin signalling is central to development and its regulation is essential in preventing cancer. Using phosphorylation of Dishevelled as readout of pathway activation, we identified Drosophila Wnk kinase as a new regulator of canonical Wnt/β-catenin signalling. WNK kinases are known for regulating ion co-transporters associated with hypertension disorders. We demonstrate that wnk loss-of-function phenotypes resemble canonical Wnt pathway mutants, while Wnk overexpression causes gain-of-function canonical Wnt-signalling phenotypes. Importantly, knockdown of human WNK1 and WNK2 also results in decreased Wnt signalling in mammalian cell culture, suggesting that Wnk kinases have a conserved function in ensuring peak levels of canonical Wnt signalling.