The purpose of this article is to raise the awareness of veterinary specialists in the field of treatment and prevention of lymphoma in cats, as well as to give an example of the effectiveness of treatment of lymphoma with chemotherapy, according to the modified CHOP protocol. The patient is an 11-month-old half-breed cat. The reason for going to the clinic: lameness for several days and serous discharge from the nose. X-ray examination, computed tomography, cytological analysis using the method of material selection using fine needle biopsy (TIAB), general and biochemical blood tests, rapid test for the presence of leukemia and immunodeficiency viruses (FIV AB/FeLV Ag) were used as methods of diagnosing the disease. The treatment was carried out from the age of 11 months to one year and nine months. The treatment protocol is given in details. The article provides a general information of feline lymphoma, describes its types and clinical picture, recommended treatment regimens and prognosis, provides information on the average life expectancy of cats with lymphoma with timely and prompt treatment.