The tribe Microcentrini Deitz 1975 (Hemiptera: Membracidae: Stegaspidinae) is revised. The four genera (Centroflexus, new genus; Centruchoides Fowler 1896; Microcentrus Stål 1869; Tumecauda Goding 1930) and 25 species included in the tribe are described (or redescribed) and illustrated based on adult and nymphal morphology. Centroflexus has one valid species, Centroflexus fasciatus, n.sp. Centruchoides has two valid species. Microcentrus has 18 valid species, including 9 new species: M. alius, M. astales, M. cyclocarinatus, M. diabolus, M. incomptus, M. lunatus, M. solussidus, M. vespertiliauris, and M. webbi. Tumecauda has four valid species, including T. pygmaea, n.sp. A lectotype is designated for Uroxiphus caryae Fitch 1851 (now in Microcentrus). New synonymies are: Glischrocentrus Fowler 1896, a junior synonym of Microcentrus [with the new combination Microcentrus cucullatus (Fowler, 1896)]; Microcentrus auritus Ball 1933, a junior synonym of M. lynx Ball 1933; Dontonodus Funkhouser 1930, and Disconotus Strümpel, 1988, junior synonyms of Tumecauda [with new combinations T. magnifica (Strümpel 1988) and T. serraticornis (Funkhouser 1930), and reinstated combination T. schaefferi Goding 1930]. Results of a morphology-based phylogenetic investigation of basal treehopper relationships are presented. Parsimony analyses of these data suggest the following assertions: (1) The monophyly of Microcentrini is supported by at least one synapomorphic character. (2) Microcentrini and Stegaspidini are monophyletic sister tribes. (3) The unplaced genera Antillotolania and Deiroderes are affiliated with Stegaspidinae. (4) The unplaced genus Holdgatiella is closely affiliated with Nicomiinae. Revised definitions are given for the subfamily Stegaspidinae and the tribe Microcentrini.