The purpose of the study reported here, to investigate the effect of atropine on cardio-respiratory parameters and body temperature in cats undergoing ovariohysterectomy with the combination of medetomidine-ketamine anesthesia. Twenty-six adult female intact domestic cats were admitted to Ankara University Faculty of Veterinary Medicine, Department of Obstetrics and Gynecology for routine elective ovariohysterectomy. The animals were divided into two groups by the randomized grouping method before the operation. Trial animals (n=14) received atropine together with medetomidine and ketamine anesthesia. In control animals (n=12) received the same anesthesia without atropine injection. At the end of the operation, animals were moved to the critical care unit and the measurements of vital parameters were performed. Heart, respiration rates, deep rectal temperature and status of anesthesia recovery were recorded after the operation every 10 minutes for 1 hour.There was a group, time, and group x time interaction noted for heart rate. Treatment cats showed greater heart rate during measurement. The mean respiratory rate and deep rectal temperature were in reference ranges for cats and similar for both groups. In both groups significant sedation induced, however, the scores were not statistically significant among groups.In conclusion, atropine is an effective drug preventing decrease of heart rate and patients have shown less undesirable side effects when it is used before the administration of medetomidine in cats that operated for ovariohysterectomy.