[Formula: see text] production at lepton colliders: a new hope for heavy neutral leptons

We present the first study of the production of a Standard Model Higgs boson at a lepton collider in association with a pair of W bosons, [Formula: see text] , in the inverse seesaw model. Taking into account all relevant experimental and theoretical constraints, we find sizable effects due to the additional heavy neutrinos up to [Formula: see text] on the total cross-section at a center-of-mass energy of 3 TeV, and even up to [Formula: see text] with suitable cuts. This motivates a detailed sensitivity analysis of the process [Formula: see text] as it could provide a new, very competitive experimental probe of low-scale neutrino mass models.