The spider genus Peucetia includes 54 species of medium-sized and widely distributed spiders. The majority of its species occurs in the tropical regions, of which only the African fauna has been recently revised. In the Neotropical Region 26 species were described, of which 17 are here synonymyzed. Peucetia tranquillini Mello-Leitão 1922, P. rubrigastra Mello-Leitão 1929, P. meridionalis Mello-Leitão 1929, P. villosa Mello-Leitão 1929, and P. viridisternis Mello-Leitão 1945 are considered junior synonyms of P. flava Keyserling 1877. Eight names, Peucetia similis Keyserling 1877, P. amazonica Mello-Leitão 1929, P. heterochroma Mello-Leitão 1929, P. maculipedes Piza 1938, P. trivittata Mello-Leitão 1940, P. duplovittata Mello-Leitão 1941, and P. roseonigra Mello-Leitão 1943 and Tapinillus argentinus Mello-Leitão 1941 are considered junior synonyms of P. rubrolineata Keyserling 1877. Both senior species are extremelly common, occurring from Colombia to northern Argentina. Peucetia macroglossa Mello-Leitão 1929, recorded only from Central Brazilian Amazonia and Guyana is considered a senior synonym of P. melloleitaoi Caporiacco 1947. Two species occur from Southern USA to northern Colombia: Peucetia viridans (Hentz 1832) and P. longipalpis F. O. P.-Cambridge 1902. The former is recognized as a senior synonym of P. poeyi (Lucas 1857), P. bibranchiata F. O. P.- 1902 and P. rubricapilla Petrunkevitch 1925 and the later as a senior synonym of P. cauca Lourenço 1990. Peucetia viridis (Blackwall 1858), known from Africa, southern Spain and Middle East is newly recorded from the West Indies. One new species, Peucetia cayapa sp. n., is described and illustrated based on males and females from Ecuador and Peru. Peucetia caldensis Garcia-Neto 1989, from Brazil, is transferred to Tapinillus Simon 1898. The type specimens of three species, P. quadrilineata Simon 1891 and P. thalassina (C. L. Koch 1847) from Central America, and P. smaragdina Mello-Leitão 1941 from Colombia are probably lost. Since their original descriptions are not sufficiently clear for their recognition, they are considered nomina dubia.