A 9-year-old female mixed-breed dog presented with alopecia, squama, scaling, erosion, and hyperpigmentation that had persisted for three months. Histopathological assessment of a skin biopsy, bone marrow aspiration, and fine needle aspiration of the liver and spleen revealed lymphocyte hyperplasia. A blood cell count also indicated severe lymphocytosis. These findings were consistent with lymphocytosis accompanied by cutaneous lesions, and not neoplastic proliferation of lymphocytes or any other pathology. The dog was treated with antibiotic, antimycotic, dietary therapy, and interferon therapy, and achieved remission of skin lesion and lymphocytosis on steroid therapy.