Species richness and composition of the metazoan parasite communities of 2 ictalurid catfishes (yellow bullhead [Ameiurus natalis] and channel catfish [Ictalurus punctatus]) were compared from within the Big Thicket National Preserve in southeastern Texas, U.S.A., to areas outside the preserve. Ninety-five fishes were sampled from 2009 to 2013 from 6 sites each inside and outside the Preserve, and 31 species of parasites were recovered (27 species from inside and 14 species from outside). Comparison of species accumulation curves utilizing recently developed methods demonstrated significant differences in the species richness and composition, the abundance distributions for parasite communities as a whole, or both, and of the community of channel catfish considered alone. Additional univariate and multivariate analyses and observations confirmed significant differences in the species composition and abundance of these parasite communities. The parasite community inside the Preserve is dominated by adult endohelminths representing both ictalurid specialists that are either absent or less abundant outside the Preserve. Additionally, generalist parasites more commonly parasitizing other fishes were more speciose and abundant inside the Preserve. The differences observed in the present investigation suggest that the waters of the Big Thicket National Preserve harbor more diverse and abundant fish, invertebrate communities, or both, thus leading to higher diversity and abundance of their parasite communities.