Red grouper (Epinephelus morio) modify their habitat by excavating sediment to expose rocky pits, providing structurally complex habitat for many fish species. Surveys conducted with remotely operated vehicles from 2012 through 2015 were used to characterize fish assemblages associated with grouper pits at Pulley Ridge, a mesophotic coral ecosystem and habitat area of particular concern in the Gulf of Mexico, and to examine whether invasive species of lionfish (Pterois spp.) have had an effect on these assemblages. Overall, 208 grouper pits were examined, and 66 fish species were associated with them. Fish assemblages were compared by using several factors but were considered to be significantly different only on the basis of the presence or absence of predator species in their pit (no predators, lionfish only, red grouper only, or both lionfish and red grouper). The data do not indicate a negative effect from lionfish. Abundances of most species were higher in grouper pits that had lionfish, and species diversity was higher in grouper pits with a predator (lionfish, red grouper, or both). These results may indicate that grouper pits are a favorable habitat for both lionfish and native fish species or that the presence of lionfish is too recent to have caused changes to fish community structure.