Predator effects on prey traits change competitive interactions between prey species affecting resource use. Parasitic phorid flies limit competitive-dominant ant activity, potentially meditating competitive interactions between ant species, changing competitive hierarchies, or affecting ant communities. I considered interactions between phorids (Pseudacteon sp.), their ant host (Azteca instabilis F. Smith), and co-occurring ant species in coffee agro-ecosystems testing whether phorids (1) limit A. instabilis recruitment activity, (2) affect competitive interaction between ant species, and (3) are associated with other species’ resource access and therefore have the potential to change competitive hierarchies. I monitored recruitment of A. instabilis and other ants to baits over 90 min on canopy trees with or without phorids. A. instabilis were one-half as abundant with phorids. Other species gained access to baits 12 times more often and were only able to take over baits when phorids were present. Furthermore, many more species (13 versus 2) gained access to resources when phorids were present. These results indicate that phorids mediate competitive interactions between ant species and may influence ant communities by affecting resource availability. Considering that phorids limit A. instabilis attacks on herbivores and that ant species differ in effects on arthropod communities, phorids may have strong community-level effects in coffee agro-ecosystems.