Cutaneous sterile pyogranuloma/granuloma syndrome (SPGS) is a locally restricted multinodular dermatitis. Affected dogs are typically healthy, but a few show systemic signs. Herein, a case of a dog presenting with generalized ulcerative dermatitis with systemic signs of mild anemia and an increased C-reactive protein level is described. Cutaneous SPGS was diagnosed by histopathology, negative staining causative organisms, and polymerase chain reaction for Mycobacterium spp. Successful treatment was achieved by immunosuppressive drugs, including prednisolone and azathioprine, administered for at least 20 mo. Recurrences of skin lesions were observed when prednisolone and/or azathioprine were discontinued. Long-term management with immunosuppressive agents may be required if the affected dog exhibits severe symptoms of cutaneous SPGS.