A one and a half-year-old, male, castrated, domestic short-haired cat was presented with a six‑month history of depression, anorexia, skin lesions, excessive itching and systemic lymphadenopathy. Complete blood count revealed severe leukocytosis (114,700 cells/μl), and peripheral blood films were characterized by marked lymphocytosis. Lymph nodes examinations and bone marrow aspirate were not suggestive of neoplastic changes. Histopathologic examination of skin lesions revealed allergic dermatitis. Based on the anamnesis and histopathologic features, non-flea, non-food hypersensitivity dermatitis (NFNFHD) was diagnosed. Treatment was initiated with prednisolone and cyclosporine. During the treatment, the cat fully recovered from the skin lesions. Leukocytosis was reduced to 18,940/μl six months after initiation of medication. To the authors’ knowledge, this is the first report describing a case of a leukemoid reaction secondary to feline NFNFHD.