The present note describes the occurrence of Monticellius indicum Mehra, 1939 (Digenea: Spirorchiidae) in an adult loggerhead turtle, Caretta caretta (Linnaeus, 1758), found on the coast of the state of Rio de Janeiro, Brazil. Pathological changes due to spirorchiid eggs (type 1 and 3) were found in gastrointestinal system, endocrine system, and heart. This parasite has previously been described in the green turtle, Chelonia mydas (Linnaeus, 1758), from Pakistan, Brazil and Costa Rica as well as in the hawksbill sea turtle, Eretmochelys imbricata (Linnaeus, 1766), in Brazil. This note reports the loggerhead turtle as a new host for M. indicum. [ABSTRACT FROM AUTHOR]