The minute, cleptoparasitic bee genus Chiasmognathus (Nomadinae: Ammobatini) is documented from western Kenya, representing the southernmost records of the lineage. Two species are recognized from the Great Rift Valley—Chiasmognathus aturksvenicus, from the southwestern side of Lake Turkana, and the other, C. riftensis, from further south near Lake Bogoria. The former was captured in association with its host, Nomioides (Nomioides) turanicus (Halictinae: Nomioidini). Chiasmognathus saheliensis is considered a new junior synonym of Pasites gnomus, and the latter epithet is transferred to Chiasmognathus: C. gnomus. We illustrate and discuss intraspecific variation in some morphological features of these tiny bees.