Four new species of fleas of the genus Ctenidiosomus Jordan, 1931, are described from Puntarenas and San Jose provinces, Costa Rica and the Piura and Cuzco regions of Peru (Ctenidiosomus eckerlini, Ctenidiosomus churchi, Ctenidiosomus pattersoni, and Ctenidiosomus solusensus). This is the first record of the genus in Central America. Four specimens of C. eckerlini were collected from three different host species (Peromyscus mexicanus (Saussure, 1860), Nephelomys devius (Bangs, 1902) and one from a composite of three different hosts (none of which it had ever been collected from previously). The preferred host for the new Peruvian species C. churchi, appears to be Thomasomys cinereus Thomas, 1882, although additional collections are needed to validate its true host. Ctenidiosomus pattersoni occurred on Lestoros inca (Thomas, 1917) but was most abundant on Akodon torques (Thomas, 1917). The fourth new taxon, C. solusensus, was described from two females, one collected from Akodon aerosus Thomas, 1913, and the other from Nephelomys levipes (Thomas, 1902). All known records of Ctenidiosomus were from species belonging to the rodent family Cricetidae with two exceptions from an opossum shrew, Caenolestes fuliginosus (Tomes, 1863) and L. inca. Table 1 identifies the documented host species for the nine known species. The genus Ctenidiosomus was known previously only from South America (Venezuela to Argentina) and is the only member of the family Pygiopsyllidae in the Western Hemisphere. Except for Ctenidiosomus perplexus Tipton and Machado-Allison, 1972, there are only a few records for each of the other eight species of this geographically enigmatic genus that spans the entire length of the western Neotropical Region. Considering the diversity of host records (n = 23), individual species have seldom been recovered from the same host species. The presence of setae on the aedeagus is pointed out for the first time in the genus. A discussion of the origin, phylogenetic relationship to Australian pygiopsyllids, its presence in the New World, and host associations for the genus are discussed; however, conclusive evidence remains unclear and requires further investigation.