Abstract We consider an isolated electroweak monopole solution within the Standard Model with a nonlinear Born–Infeld extension of the hypercharge gauge field. Monopole (and dyon) solutions in such an extension are regular and their masses are predicted to be proportional to the Born–Infeld mass parameter. We argue that cosmological production of electroweak monopoles may delay the electroweak phase transition and make it more strongly first order for monopole masses $$M\gtrsim 9.3 \,{\cdot }\, 10^3$$ M ≳ 9.3 · 10 3 TeV, while the nucleosynthesis constraints on the abundance of relic monopoles impose the bound $$M\lesssim 2.3\cdot 10^4$$ M ≲ 2.3 · 10 4 TeV. The monopoles with a mass in this shallow range may be responsible for the dynamical generation of the matter–antimatter asymmetry during the electroweak phase transition.