An adult male blue and gold macaw (Ara ararauna) was presented for evaluation of a right periorbital mass. Results of diagnostic tests, including periorbital ultrasound, fine-needle aspirate, and cytologic examination, confirmed a diagnosis of periocular lymphoma. Radiographs were suggestive of disseminated disease but because of concerns about the patient's quality of life, localized radiation therapy to address the periorbital disease was pursued. Coarse-fractionated radiation therapy was initiated, and the mass regressed rapidly during the 3-week course of treatment. The macaw tolerated the treatments well, maintained vision in the affected eye, and activity level and appetite improved. Three months after treatment was completed, the bird died. Necropsy revealed T-cell-rich B-cell-infiltrative lymphoma of the spleen, liver, and kidneys, with some residual neoplastic cells found in the right periorbital region. This case demonstrates a radiation therapy protocol that reduced a tumor mass in a localized treatment of periorbital lymphoma in a macaw.