The Neotropical psittacine species Amazona aestiva, commonly known as the blue-fronted Amazon, is one of the most common and best-known psittacine birds kept as a pet worldwide. However, very little is known about the diseases or parasites of these birds. In this study, we describe a new species, Eimeria aestivae, associated with these parrots. The new species is characterized by: ovoid smooth oocysts (n  =  60), 36.8 (33.2–41.5) × 23.7 (21.7–25.7) µm, length/width ratio  =  1.55; polar granule present; ellipsoidal sporocysts (n  =  25), 19.8 (17.5–21.6) × 9.3 (8.3–9.9) µm; Stieda, sub-Stieda body, and sporocyst residuum present. Sporozoites (n  =  20), 2 per sporocyst, elongate and curved, 17.6 (15.8–19.2) × 3.8 (3.2–4.8) µm; each with 2 refractile bodies. The oocysts of the other 2 eimerian species described for Amazona are larger than those of the presented species, but they all seem to be closely related because of some similarities among them.