The Nearctic species of the genus Trichacis are revised. Nine out of 15 species recognized are new to science: T. alticola (New Mexico, Colorado), T. bison (Ontario, Florida, Louisiana, Illinois, Texas), T. celticola (Mississippi, Ontario, Louisiana, Texas), T. dracula (Illinois), T. elongata (Missouri), T. huberi (California), T. mandibulata (Illinois), T. pyramidalis (Ontario), and T. striata (Florida). Six previously described Nearctic species are redescribed, viz. T. arizonensis (Ashmead), T. cornicola (Ashmead), T. cornuta Fouts, T. rufipes Ashmead, T. texana Fouts, and T. virginiensis Ashmead. The males of T. arizonensis, T. texana, and T. virginiensis are described for the first time. A generic diagnosis of Trichacis and keys to Nearctic species are given. The higher classification, bionomics, world distribution, and character states of Trichacis species are discussed.