Coccidiosis is a devastating worldwide disease and is considered a dreadful disease in lovebirds. Indeed, a problem has been appeared cocktail lovebirds kept in a private pet birdhouse in Sheikh Zayed City, Giza, Egypt, in the shape of blood-tinged diarrhea, birds huddled together and showing signs of inappetence, ruffled feathers, unable to fly, general weakness and emaciation associated with high mortalities. Therefore, this study aimed to diagnose and find a suitable treatment to overcome such problems. To achieve this aim, blood and droppings samples were collected from infected and healthy birds for parasitological and hematological examinations, and tissue samples were collected from freshly dead birds for postmortem and histopathological examinations. A treatment trial was adopted on 50 infected birds and 25 healthy and parasitological negative birds and groups were classified as follows: group 1) 25 infected birds treated with Diclazuril, group 2) infected birds treated with Coccicure, and group 3) 25 birds kept as control negative reference birds. The parasitological identification revealed the presence of Eimeria aratinga (E. aratinga) oocysts in the infected bird intestine. Finally, we concluded that E. aratinga is a serious protozoon parasite infesting lovebirds revealing severe clinical signs, high mortalities, histopathological changes in the intestine and alteration in blood parameters. Diclazuril is an effective drug in treating E. aratinga in cocktail lovebirds.