This case report describes a 38 year old wild caught male Matamata turtle housed at the Rosamond-Gifford Zoo that presented with a mass located on the dorsal aspect of the right rear limb. The turtle had been hypophagic for the past 4 weeks. Upon physical exam the turtle was weak but had not lost a significant amount of weight since the previous year (10% body weight). There was a 4 cm diameter mass on the dorsal aspect of the right thigh and stifle that seemed to have invaded into the adjacent carapace. Differential diagnoses for turtle shell lesions include infectious diseases including bacterial, viral, and fungal diseases, trauma with subsequent infection and, rarely neoplasia. Our diagnostic and treatment plan included blood collection, whole body radiographs, and ultrasound of the mass. The mass was debrided and samples of the abnormal tissues were collected and submitted for histopathologic examination, bacterial and fungal cultures. Until the results of the biopsy and culture were obtained, the wound was managed with lavage and daily bandage changes. The turtle was treated with enrofloxacin, SQ fluids, and ketoprofen. The biopsy revealed squamous cell carcinoma. Due to the Matamata's poor prognosis euthanasia was elected. The necropsy revealed metastatic squamous cell carcinoma and mild bacterial sepsis. This is only the second report of squamous cell carcinoma in turtles.