The Microcoryphia are extensively distributed in the Nearctic Region, with over 30 species in 12 genera in two families. The genus Machilinus Silvestri 1904 has previously been reported from Arizona, British Columbia, California, Nevada, Utah, and possibly Colorado. I report and describe three new species of Machilinus based on specimens from Colorado, New Mexico, Arizona, Idaho, Montana, and Nevada. Machilinus matadero, new species, was collected from June through November in metropolitan Denver, Colorado. Machilinus taoseno, new species, was collected in April through August in northern New Mexico, central Colorado, and central Arizona. Machilinus zingiberus, new species, was collected in July through August in central Idaho and northern Nevada. A few biological notes are presented for each species. The machilid Pedetontus californicus (Silvestri 1911) is reported from Idaho for the first time.