Background In Australia, guidelines for the appropriate use of antibiotic prophylaxis are provided in the Therapeutic Guidelines: Antibiotics. However, their inappropriate use remains a concern. Objective To examine adherence to therapeutic guidelines in breast surgery and to identify trends of non-adherence depending on breast surgery types. Setting Major Western Australian teaching hospital. Method A retrospective study collected data from a random sample of 150 of a total of 1049 eligible medical records of patients who underwent a breast surgical procedure in 2013 or 2014. Main outcome measure A binary classification (adhered to/not adhered to) was utilised to assess adherence of preoperative antibiotic use to the head, neck and thoracic therapeutic guidelines: antibiotic that were current at the time. Secondary analyses investigated any link between adherence to guidelines and development of an infection. Results Antibiotic prophylaxis was prescribed by 14 surgeons for 140 (92.7%) procedures. Adherence to all guidelines occurred in 20 (13.3%) procedures, whilst 11 (7.3%) did not adhere to any element of the guidelines. Appropriate timing was the main factor not adhered to occurring in 65 (43.3%) procedures. Postoperative antibiotics were prescribed in 35 (23.3%) of surgeries, with 32 (91.4%) administered beyond 24 hours. The average antibiotic course was 8.21 days. The length of stay was significantly different (p=0.0036) between surgical groups but being only statistically significantly longer (p=0.0066) in the ‘other’ surgical grouping (other than mastectomy, axillary node clearance and reconstruction). There was a tendency for risk of an infection to be decreased with compliance (odds ratio: 0.23; 95% CI: 0.05, 1.07; p= 0.06). Conclusion A gap between clinical practice and guidelines exists possibly owing to lack of specificity in the guidelines current at the time. With the update guidelines, there is hope that adherence to the guidelines will be increased. Education and guidelines based upon the Therapeutic Guidelines: Antibiotic for breast surgery needs to be implemented at the hospital.