This report describes a series of observations made on 2 parasite species infecting a collection of horned passalus beetles (Odontotaenius disjunctus, n = 135), from Georgia, U.S.A., that were collected as larvae in the wild and were reared to metamorphosis in captivity. Tachinid fly maggots emerged from 15 beetle larvae (11%) and, when they completed their development into adults, we identified them as Zelia vertebrata, a known but little-studied parasitoid of O. disjunctus. We also observed infections by Steinernema nematodes (n = 11 cases, or 8%), which killed and consumed the carcasses and which produced thousands of infective juveniles in the rearing containers. Based on morphological measurements of infective juvenile and adult worms, these nematodes were consistent with Steinernema carpocapsae, members of which infest the surface of soils and which infect a wide range of insects. This report is the first to describe Steinernema infections in O. disjunctus, and our observations of Z. vertebrata infections and prevalence will be useful for comparative purposes or future study.