A 9-year-old female spayed English Bulldog was referred to Cornell University Animal Hospital for seizures, history of coughing, and further evaluation of thoracic and abdominal masses seen on radiographs taken by the referring veterinarian. The dog had history of keratoconjunctivitis sicca, skin allergies, and urinary crystals. In September of 2018 she spent some time at a boarding facility. After coming home she developed labored breathing, cough, soft stools and decreased appetite. She was taken to a local emergency hospital and was diagnosed with kennel cough. She was placed on a one-week course of antibiotics and a cough suppressant. On October 20th the dog suffered a seizure that lasted less than three minutes. She recovered but was mildly ataxic and able to eat dinner that night. On October 22, 2018 the dog had a coughing episode and was taken to her local veterinarian for thoracic and abdominal radiographs. Radiographs showed possible thoracic and abdominal masses. Her physical exam yielded, bilateral yellow ocular discharge, increased respiratory effort, mildly distended abdomen, a small patch of alopecia on her left lateral hock and gingival hyperplasia. The remaining physical exam parameters were within normal limits. At this time she was referred to Cornell for further work–up. At Cornell her physical showed many of the same signs as well as a slightly distended abdomen, tachypnea, and mildly muffled cardiac auscultation. Once at Cornell she had a hemogram, chemistry panel, thoracic radiographs, abdominal focused assessment with sonography for trauma with sampling, thoracic focused assessment with sonography for trauma with sampling, and an echocardiogram on initial workup. The initial cytology showed cells consistent with mesothelioma or reactive mesothelial cells. A computed tomography scan was performed to assess the extent of her disease and surgical planning. Two days later she went to surgery for a pericardectomy and biospies of enlarged intrathoracic lymph nodes. She was diagnosed with mesothelioma based off histopathology from her mediastinal lymph node and verified with immunohistochemistry. This senior seminar will cover and discuss the presentation, possible differentials, diagnosis, treatment, and prognosis of mesothelioma in dogs.