This article reviews the capniid genus Paracapnia Hanson and describes a new species, P. boris, from males and females collected in northern California, provisionally assigned to the genus. Paracapnia oswegaptera (Jewett) is placed in synonymy with P. ensicala (Jewett), and the first description is provided for the male of P. disala (Jewett). Keys are presented for recognized Palearctic and Nearctic members of the genus. Distribution data are given for specimens examined and for those in the published literature.