Sertoli cell tumors are primary testicular neoplasms that can present with a variety of clinical signs that may include certain paraneoplastic syndromes. To date, orchiectomy has been the only treatment option mentioned in the literature for avian species. Due to the difficult anatomic location of the testes in birds and the potential for metastasis, this is not always a viable option. This report describes a Mallard with a Seroli cell tumor that was not amenable to surgical removal and was treated with carboplatin chemotherapy. This and other forms of chemotherapy may prove to be useful in the treatment of these tumors in birds, and should be explored further.