Diffuse iris melanoma is uncommon, but is the most common primary intraocular neoplasia in cats.1,2 The diagnosis can be difficult to make, and determining an appropriate prognosis can be nearly impossible. Treatment options associated with this disease are quite limited, and the best care for these patients is achieved on a case-by-case basis. There is a need for further research and investigation to help assist us in the care of these patients. This case report will focus on the clinical presentation, diagnosis, treatment options, and prognosis of diffuse iris melanoma in an approximately 8-year-old, castrated male, domestic shorthair cat.