In this report, it is aimed to notify clinical, haematological and biochemical changes due to deltamethrin intoxication in a 10-month-old female, tabby cat. The material of the case was a 10-month old, female tabby cat. The cat had the complaints of difficulty in standing, stretching the legs to the sides and doing abnormal moves. These complaints occurred after the cat licked its kittens which were sprayed with a watery solution of a pesticide called K-Othrine SC 50 that contains deltamethrin that is used against intense lice infestation which is frequently seen in the kittens. Haematological and biochemical analyses were performed on the blood sample. In the physical examination of the cat; Incoordination, spontaneous contractions, ataxia, hyperesthesia, hypothermia (T:37.2°C), tachycardia (128/min) and mydriasis were detected. Hematologic examination revealed leukocytosis (24.81x103/μL) and neutrophilia (21.38x103/ μL). Biochemical analysis showed an increase in ALT, AST, ALP, LDH and CK-MB activities and cholesterol, glucose, calcium and potassium levels. Since there was no specific antidote to deltamethrin toxicity, 0.9% NaCl and 5% dextrose solution were administered intravenously at a dose of 40 ml/kg and diazepam at a dose of 0.5 mg/kg. 5 mg/kg enrofloxacin was administered subcutaneously. In the treatment of hypothermia blankets and hot water bottles were used. According to the information obtained from the owner, it was learned that the cat regained its health. In this case report, attention was drawn to clinical, haematological and biochemical changes in deltamethrin toxicity in cats. Also, it was concluded that the prognosis of deltamethrin toxicity was generally very good with prompt and effective treatment.