Caecincola septimus n. sp. is described from the intestine of largemouth bass (Micropterus salmoides) collected from Turkey Creek and Menard Creek in the Big Thicket National Preserve, Texas, U.S.A. Members of the new species are most easily distinguished from Caecincola longiscens and Caecincola cookorum by having ceca that do not extend past the anterior testis or into the posttesticular space, and from the remaining species in the genus (Caecincola autumnae, Caecincola latostoma, Caecincola parvulus, and Caecincola wakullata) by a combination of body size and shape, arrangement of the testes, number of ovarian lobes, and size of the oral sucker. This is the fourth species of Caecincola described from largemouth bass, the others being C. parvulus from Wisconsin, C. wakullata from Florida, and C. latostoma from Louisiana.