A total of 475,431 mosquitoes representing 8 genera and 43 species were collected from a marsh in the western Kenya highlands to determine species composition and succession in relation to the epidemiology of Rift Valley fever virus. Culex pipiens was the most common species, totalling 92.3% of the collection, followed by Cx. zombaensis (2.2%), Anopheles coustani (1.1%), An. squamosus (0.8%), Mansonia uniformis (0.6%), Coquillettidia microannulatus (0.5%), Uranotaenia mashonaensis (0.5%), Ma. africana (0.4%) and Cq. aurites (0.4%). Aedes quasiunivittatus was the first floodwater species to emerge from newly flooded areas and was the most abundant Aedes collected, representing 88% of all Aedes specimens. Culex guiarti and Cx. zombaensis colonized newly flooded areas soon after the areas became flooded.