Philornis is a neotropical genus of muscid fly that interacts with birds and may affect the development and survival of the birds' offspring. Although Philornis is a relatively common parasite, there is a lack of information about Philornis hosts in several parts of the Americas. In this study, two nests of the Rufousfronted Thornbird (Phacellodomus rufifrons) were collected in Pedro Leopoldo, southeast Brazil. The first contained four nestlings of advanced age (about 20 d old) and a recently emerged Philornis torquans female adult fly. The second nest contained three nestlings (less than 7 d old) and several Philornis torquans subcutaneous larvae. One of the nestlings was infested by 53 larvae, which had attacked several parts of its body and caused individual wounds containing 1 to more than 15 larvae. The length of the larvae ranged from 3 to 18 mm and only one was a second instar; the remaining 69 were third instars. The pupal period lasted 9–13 d. In total, 71 larvae were collected from the nest, with nestling parasitism varying from 7 to 53 larvae (mean- 23.7±25.5 larvae/nestling).