A 26-year-old, male eclectus parrot (Eclectus roratus) was presented to its primary care veterinarian for a 10-day history of increased respiratory effort, lethargy, and a single episode of regurgitation. Hepatomegaly, proventricular enlargement, cranial displacement of the ventriculus, and coelomic effusion were suspected based on a 1-view radiographic image, and the patient was referred for further evaluation. On presentation to the referral veterinary hospital, a distended coelom and dyspnea with abnormal respiratory sounds were abnormalities noted upon physical examination of the patient. The bird was hospitalized for supportive care, and diagnostic tests were performed. Initial radiographic images at the referral hospital revealed a large intracoelomic mass. A computed tomographic scan was performed; however, the origin of the mass could not be determined. A fine-needle aspirate and cytologic evaluation of the intracoelomic mass revealed a neoplastic process but no specific tissue type. Two days after presentation to the referral hospital, an exploratory coeliotomy to surgically resect the mass was attempted. The mass occupied most of the coelomic cavity, with multiple adhesions to internal organs. The mass was successfully resected; however, the patient destabilized and died despite resuscitation efforts. Histopathologic examination of submitted tissue from the mass with immunohistochemistry revealed mixed populations of neoplastic cells differentiated from 3 primordial germinal layers, confirming the diagnosis of teratoma. Teratomas appear to be a rare tumor in avian species but should be included in a list of differential disease diagnoses for abnormal tissue masses of unknown origin. Only 2 cases of teratomas have, to our knowledge, been reported in psittacine species.