Species of the genus Sadocus Sørensen, 1886 are conspicuous gonyleptids that occur in Chile and Argentina. Here, the genus is revised for the first time and the cladistic analysis based on morphological characters does not corroborate its monophyly unless a phylogenetically unrelated species is excluded (explained further on). A new classification is proposed for the seven species left in the genus and considered valid, of the 13 nominal species previously recognized. Two out of the seven valid species are considered as species inquirendae: Sadocus allermayeri (Mello-Leitão, 1945) [= Carampangue allermayeri Mello-Leitão, 1945] and Sadocus nigronotatus (Mello-Leitão, 1943) [= Carampangue nigronotatum Mello-Leitão, 1943]. The following synonymies are proposed: Sadocus bicornis (Gervais, 1849) [original combination = Gonyleptes bicornis Gervais, 1849] is a junior synonym of Sadocus asperatus (Gervais, 1847) [= Gonyleptes asperatus Gervais, 1847]; Sadocus conspicillatus Roewer, 1913, Sadocus exceptionalis (Mello-Leitão, 1946) [= Araucanoleptes exceptionalis Mello-Leitão, 1946] and Sadocus guttatus Sørensen, 1902 are junior synonyms of the valid name Sadocus polyacanthus (Gervais, 1847) [= Gonyleptes polyacanthus Gervais, 1847]; and Sadocus calcar (Roewer, 1913) [= Lycomedes calcar Roewer, 1913] is a junior synonym of the valid name Gonyleptes horridus Kirby, 1819. Sadocus brasiliensis Soares & Soares, 1949 is not congeneric with Argentinean/Chilean species of the genus according to the cladistic analysis and is here synonymized with Discocyrtus catharinensis (Mello-Leitão, 1923 [= Sadocus catharinensis Mello-Leitão, 1923]).