The spumarius species-group of Nearctic PachybrachisChevrolat, 1836 is defined and revised. The group is composed of one species: Pachybrachis spumariusSuffrian, 1852. A male specimen of P. spumarius, recently discovered in the Natural History Museum in London among some previously unrecognized type material of Suffrian, is herein designated as a lectotype. The synonymy of Pachybrachis roborisFall, 1915 with P. spumarius is confirmed, and Pachybrachis obfuscatusFall, 1915 is synonymized under P. spumarius, new synonymy. A description, figures, and range map are presented.