This poster presents the search for new resonances decaying into a W boson and a 125GeV Higgs boson in the lvbb final state, where l=e+- or mu+-, in pp collisions at root(s)=13TeV. The search includes a channel requiring one lepton and missing transverse energy, as well as a channel with only missing transverse energy for the case where the lepton is not reconstructed. The data used correspond to a total integrated luminosity of 139fb-1 collected with the ATLAS detector at the Large Hadron Collider with the full Run-2 dataset. The search is conducted by examining the reconstructed invariant and transverse mass distributions of Wh candidates for evidence of a localized excess in the mass range of 400GeV up to 5TeV. Upper limits are placed at the 95% confidence level on the production cross-section times branching fraction of heavy W' resonances in heavy-vector-triplet models.