Some organisms in this order include: Species in this order typically have four to six flagella at the cell's apical pole, one of which is recurrent - that is, it runs along a surface wave, giving the aspect of an undulating membrane.

Like other parabasalids, they typically have an axostyle, a pelta, a costa, and parabasal bodies.

In Histomonas only one flagellum and a reduced axostyle are found, and in Dientamoeba, both are absent.

Trichomonads reproduce by a special form of longitudinal fission, leading to large numbers of trophozoites in a relatively short time.

Cysts never form, so transmission from one host to another is always based on direct contact between the sites they occupy.