Background: Cesarean section is a procedure for taking the fetus in the womb through the incision of the abdominal wall of the lower uterine segment. This procedure has a risk of infection in the operating area 5 - 20 times greater than normal labor. The risk of infection in the operating area can be reduced by giving prophylactic antibiotics. This study is needed to evaluate the accuracy of the use of prophylactic antibiotics in patients undergoing the cesarean section procedure. Methods: The study was conducted non-experimental (observational) on 118 cases of patients obtained from retrospective data. The design of the analysis used is descriptive method while the evaluation method uses Gyssens diagram. Result: The results of the analysis of 118 cases with the highest percentage; 1. Profile of the patient; age of patients 20-34 years (60.2%), gestational age 37-41 weeks (93.2%), history of second pregnancy (36.4%), history of once-childbirth (39%), no previous cesarean history (75.4) and history of cesarean delivery as the most indications for cesarean section (20.3%). 2.Prescribing profile; prophylactic antibiotics prescribed ceftizoxim 1 gram (67%), IV administration route (100%), prophylactic antibiotic time <60 minutes before surgery (46.6) and duration of prophylactic antibiotics for 12-24 hours (45.8%) . The evaluation results with the Gyssens diagram obtained 118 prescriptions included in category IV A, namely there were other antibiotics that were more effective even though the therapeutic outcome was good. Conclusion: Qualitative evaluation of the use of prophylactic antibiotics with the Gyssens method in the case of cesarean section in the obstetrics and obstetric wards of Yogyakarta City Hospital in January - June 2017 obtained the accuracy of prophylactic antibiotics in 118 patients in category IV A which meant that there were other antibiotics more effective despite good patient outcomes .