Health service delivery is an important component of a well-functioning health system. To achieve a competitive healthcare system, healthcare should be provided on time to avoid delays that could harm the patient. In this respect, patient wait time is an important indicator of health services delivery performance. Countries develop national or regional booking systems to manage patient wait times and healthcare delivery resources more efficiently. In this study; the effect of a national booking system on outpatient wait times in Turkish public healthcare settings was investigated. This study was conducted using anonymized national outpatient data sets for the year 2016 with permission from the Republic of Turkey Ministry of Health. The data was analyzed after pre-processing and transformation. As a result of the study, patient wait times were calculated, analyzed and evaluated according to province and facility care levels (secondary or tertiary). Results showed that in 2016, only 30.69% of outpatient visits had appointments and that the average waiting time for patients with appointments was 11.18% shorter than for patients without appointments. The results of this study fill a gap in the literature as almost no studies have investigated this issue due to a lack of administrative and clinical data and will provide important evidence for the improvement of health service delivery systems.