A dog being treated for brain inflammation with immune-suppressing drugs developed a serious skin infection caused by two unusual fungi not previously reported together in veterinary medicine. The infection proved difficult to diagnose, requiring tissue samples and specialized laboratory testing to identify the fungi and determine which antifungal drugs would work best. Despite treatment with antifungal medications and reducing the immunosuppressive drugs, the infection did not improve and the dog’s underlying condition worsened, ultimately requiring euthanasia. This case shows the serious risks of fungal infections in animals on long-term immunosuppressive therapy and highlights the need for careful monitoring and early detection.