The buff-footed antechinus (Antechinus mysticus) is a newly described carnivorous marsupial from eastern Australia. We examined the diet composition and prey preference of this little known dasyurid in the southernmost (Brisbane) and northernmost (Eungella) populations. Animals were captured over three months (July–September) during 2014 encompassing the breeding period (late July and August) of the species. Seasonal sampling carried over into a second year which followed the succeeding cohort of juveniles as they dispersed from their maternal nest (summer), through their maturation (autumn), to the beginning of breeding (winter), sampling across one complete generation. The diet of A. mysticus consisted predominantly of invertebrates, with 16 prey orders identified (11 Insecta, two Arachnida, two Myriapoda, one Crustacea). Vertebrate (Family Scincidae) consumption was recorded in low abundance at both sites. The diet of A. mysticus was dominated by Araneae (spiders), Blattodea (cockroaches) and Coleoptera (beetles). Comparison of identified prey consumption in scats with prey availability in pitfall traps showed A. mysticus to be a dietary generalist, opportunistically consuming mostly invertebrate prey with supplementary predation on small vertebrates. Juvenile A. mysticus preyed predominantly on Blattodea (33.4% mean percentage volume) and Coleoptera (31.6% mean percentage volume), potentially suggesting a preference for larger, easier to catch, prey items. Further exploration into the relationship between prey and body size is required to determine this.