Since its original description, the theraphosid spider genus Crassicrus Reichling & West, 1996 has not been revised and no new species have been described. While reviewing material deposited in the Mexican National Collection of Arachnids (National Autonomous University of Mexico, Mexico City) and the American Museum of Natural History (New York, USA), we encountered specimens corresponding to four new species of Crassicrus from Mexico. In this revision, we include a redescription of the genus and its type species, C. lamanai Reichling & West, 1996, and describe four new species: C. bidxigui, C. tochtli, C. cocona, and C. yumkimil. Species habitat data are provided, as well as identification keys for males and females. In addition, new keels on the male embolus were identified and are described. In the Theraphosinae, the presence of one retrolateral keel has been reported, but in Crassicrus, there are two or three retrolateral keels, and a new taxonomical nomenclature for these keels is proposed. The genus Crassicrus is recorded from Mexico for the first time, increasing the number of known theraphine genera in the country to 16.