A 5 yr old intact female cocker spaniel dog weighing 7.8 kg was referred with anorexia, vomiting, and depression. At referral, the dog was diagnosed initially with typical hypoadrenocorticism, and 2 d later, concurrent primary hypothyroidism was detected. Hormonal replacement therapies, including fludrocortisone, prednisolone, and levothyroxine, were initiated, but a few days later the dog became abruptly tachypneic, and thoracic radiographs indicated the development of pulmonary edema. Echocardiography showed that there were abnormalities indicating impaired left ventricular function, although the heart valves were normal. Following treatment with pimobendan and furosemide, the pulmonary edema resolved. The dog had no recurrence of the clinical signs after 10 mo of follow-up, despite being off all cardiac medications; consequently, the cardiac failure was transient or reversible in this dog. The case report describes the stepwise diagnosis and successful treatment of cardiogenic pulmonary edema after initiation of hormonal replacement therapy for concurrent hypoadrenocorticism and hypothyroidism in a dog.