Dietary differentiation can be a key mechanism for the coexistence of syntopic species with similar niches. On the Caribbean island of Puerto Rico, three species of bat from the family Mormoopidae — the Antillean ghost-faced bat (Mormoops blainvillei), sooty mustached bat (Pteronotus quadridens), and Parnell's mustached bat (Pteronotus parnellii portoricensis) — are aerial insectivores that roost in the same caves. To investigate the possibility of dietary differentiation, we estimated the percent volume and percent frequency of occurrence of the orders of arthropods consumed by these three species of bat, using standard fecal analysis. We also compared dietary diversity among species, as well as the amount of dietary overlap, with respect to season and habitat. Lastly, this study used canonical correspondence analysis (CCA), a method of ordination, to assess the effects of species, sex, age, reproductive condition, season, and habitat on intraspecific differences in the diet of the Puerto Rican Mormoopidae. Eight orders of arthropods were found in the diet of these mormoopids, with Lepidoptera, Hymenoptera, and Coleoptera being major staples. The CCA revealed differences in diet among the three species, suggesting that dietary differentiation is at least one mechanism for coexistence. In addition, the variables habitat and season correlated significantly with the diet of M. blainvillei and P. quadridens, whereas habitat and sex correlated with the diet of P. p. portoricensis. Thus, our study shows dietary differences among the three species of Mormoopidae living in the same caves on Puerto Rico, as well as intraspecific differences within the diet of each species.