A review of the spider family Nicodamidae reveals two subfamilies, Nicodaminae and Megadictyninae, with 29 species. The Nicodaminae contains Nicodamus Simon and six new genera, Ambicodamus, Dimidamus, Durodamus, Litodamus, Novodamus and Oncodamus, from Australia, Papua New Guinea and Irian Jaya. Nicodamus is restricted to N. peregrinus (Walckenaer) and N. mainae, sp. nov.; N. peregrinus is treated as a senior synonym of Theridium semiflavum L. Koch, Centropelma bicolor L. Koch and Ozaleus tarandus Thorell. Ozaleus Thorell is confirmed as a junior synonym of Nicodamus by designation of a lectotype for the type species, O. tarandus. Durodamus contains one species: D. yeni, sp. nov. (type species). Ambicodamus contains 11 species: A. marae, sp. nov. (type species), A. audax, sp. nov., A. crinitus (L. Koch), comb, nov., A. dale, sp. nov., A. darlingtoni, sp. nov., A. emu, sp. nov., A. kochi, sp. nov., A. leei, sp. nov., A. sororius, sp. nov., A. southwelli, sp. nov. and A. urbanus, sp. nov. Litodamus contains three species: L. hickmani, sp. nov. (type species), L. olga sp. nov. and L. collinus, sp. nov. Dimidamus contains six species: D. dimidiatus (Simon), comb. nov. (type species), D. simoni, sp. nov., D. leopoldi (Roewer), comb, nov., D. arau, sp. nov., D. sero, sp. nov. and D. enaro, sp. nov. Novodamus contains two species: N. nodatus (Karsch), comb. nov. (type species) and N. supernus, sp. nov.; Linyphia melanozantha Urquhart is treated as a junior synonym of N. nodatus. Oncodamus contains two species: O. bidens (Karsch), comb. nov. (type species) and O. decipiens, sp. nov. The Megadictyninae, stat. nov., contains two genera from New Zealand, Megadictyna Dahl with M. thilenii Dahl and Forstertyna, gen. nov. with F. marplesi (Forster), comb. nov. Cladistic analysis confirms the division of the family into two subfamilies, and recognises several subgroups within the Nicodaminae: Nicodamus + Durodamus, Ambicodamus + Litodamus, and Novodamus + Oncodamus.