Small mammals are key consumers in the marsh food web and could serve as indicators of a marsh's potential to support higher-level predators. We studied how small-mammal occupancy varied among plant communities in coastal Louisiana freshwater marshes. We sampled small mammals at 36 sites on 4 different occasions during the late spring in freshwater marshes of the Mandalay National Wildlife Refuge, LA. Mammalian diversity was low; we captured only Oryzomys palustris (Marsh Rice Rats). Occupancy modeling revealed a positive association between Marsh Rice Rat site occupancy and Sagittaria lancifolia (Bulltongue Arrowhead) biomass. Our data suggest that subtle changes in plant-species composition within a marsh may affect the distribution of the most common small mammal in the ecosystem.