BACKGROUND: The incidence of multi-drug resistant ESBL-associated urinary tract infections (UTIs) is increasing globally. Patients with abnormal renal tract anatomy and other co-morbidities are at increased risk of complicated UTI and ESBL-associated infections. The duration and safety of OPAT for this cohort of patients is unknown. OBJECTIVES: This study aims to provide an evidence base to support decision-making regarding duration of antibiotic treatment for complicated UTIs. METHODS: We retrospectively reviewed all patients receiving ertapenem with or without adjunctive fosfomycin for complicated UTIs in the OPAT service of our tertiary infectious diseases hospital. All data had been collected prospectively as part of routine clinical care. Our primary outcomes were microbiological and clinical cure of UTI. RESULTS: We identified 33 treatment episodes of ertapenem use for UTIs. 76% episodes related to pyelonephritis or urosepsis diagnoses. Renal tract abnormalities or prior urological surgery were present in 45% of patients. The median duration of appropriate parenteral antibiotic therapy in our study was 6 days. Clinical cure was achieved with short-course parenteral treatment alone in 81% of patients and this increased to 96% when adjunctive fosfomycin was used. There was a single treatment failure resulting in hospital admission. CONCLUSIONS: Short duration ertapenem via OPAT with or without adjunctive fosfomycin is safe and effective for the treatment of complicated UTIs. Further studies are required to inform optimal treatment strategies and publication of guidelines in this field.