The female genitalia of New World Cryptocephalini was studied and illustrated based on representatives of 11 of the 13 genera of the tribe. It was found that female genitalia contain pleurites IX, a rare and apparently primitive feature among leaf beetles. In other features cryptocephaline female genitalia are simpler than genitalia of other leaf beetles in having a poorly sclerotized sternite VIII and lacking the tignum. It is also hypothesized that the vagina is formed by sternites IX (dorsally) and VIII (ventrally), and that sclerotized plate of sternite IX can be homologized with vaginal palpi of flea beetles. A set of characters of diagnostic and of possible phylogenetic value was found. In general, Cryptocephalina and Monachulina bear the greatest affinity in overall morphology of the female genitalia, with Pachybrachina possessing a different set of unique morphological states. Of particular diagnostic and phylogenetic value at the subtribal level, as revealed by this study, are the shape and degree of sclerotization of tergite VIII, tergite IX, and sternite VIII.