The phylogeny of Xylosciara Tuomikoski, 1960 (type species Sciara lignicola Winnertz, 1867) and related genera was studied by parsimony analysis. Cladistic analysis of 68 morphological characters from the adults of 91 ingroup and one outgroup species produced 120 shortest cladograms. According to the most parsimonious solution, the genus was redefined as a monophyletic unit. The solution obtained supported unambiguously a close phylogenetic relationship between Xylosciara and the New Zealand taxa currently included in Corynoptera Winnertz. This result was in sharp contrast with previous hypotheses. Xylosciara is Holarctic in distribution with one known sub-Antarctic species, and the species are here keyed, described or diagnosed.