The Neotropical genus Teramocerus Schoenherr, 1840 is redefined on the basis of a taxonomic revision and of a phylogeny. In addition to several other characters of the external morphology, detailed examination of sclerites and ornamentation of the internal sac of aedeagus was used for the first time in Brentidae Billberg, 1820, providing several new characters, with also potential interest for the study of the tribe Acratini and possibly the family. Two new synonymies are proposed at generic level: Acratus Lacordaire, 1865, n. syn. for Teramocerus and Proteramocerus Kleine, 1921, n. syn. for Teramocerus. Five new species are described from Amazonian Basin and French Guiana: Teramocerus amazonicus n. sp., T. brulei n. sp., T. curtirostris n. sp., T. pulchriformis n. sp. and T. trichosternon n. sp. Because of the synonymy between Proteramocerus and Acratus with Teramocerus, seven new combinations are proposed: Teramocerus appendiculatus (Soares & Scivittaro, 1972) n. comb., T. badius Boheman, 1840, comb. rev., T. forficula (Soares & Scivittaro, 1972) n. comb., T. opacus (Perty, 1832) n. comb., T. pulcher (Soares & Dias, 1971) n. comb., T. suturalis (Lund, 1800) n. comb., and T. zellibori (Soares & Dias, 1971) n. comb. Several new synonymies are given at specific level: Acratus fidelis Kleine, 1927, n. syn. for Teramocerus badius, Proteramocerus aeneus Soares & Dias, 1971, n. syn for T. eletus Kleine, 1927, P. oliveirai Soares & Dias, 1971, n. syn. for T. eletus Kleine, 1927, P. emendatus Kleine, 1927, n. syn. for T. janthinus Boheman, 1840, P. eminens Kleine, 1927, n. syn. for T. janthinus, P. villens Soares & Dias, 1971, n. syn. for T. janthinus, Brenthus acutipennis Boheman, 1833, n. syn. for T. opacus, T. obscurus Perroud, 1853, n. syn. for T. opacus. Trachelizus helmenreichii Redtenbacher, 1868 is removed from synonymy with Teramocerus suturalis and transferred to the genus Nemobrenthus Sharp, 1895, giving the new combination Nemobrenthus helmenreichii (Redtenbacher, 1868) n. comb. Maps are provided for examined specimens of each species. An identification key is given for males and females. In a second part, a phylogenetic analysis is made to test monophyly and species assemblage of the newly defined genus Teramocerus. Maximum parsimony and Bayesian analysis were performed on a matrix of 40 morphological characters of the adults and 25 taxa; 19 were supposed to belong to Teramocerus in the meaning given here, the six others to various Acratini and Trachelizini. Both analyses show that type species of all the genera synonymized are indeed completely included in Teramocerus, this genus being then monophyletic in its new definition.