Aim: To analyze the ureteral injury and incidence of ureteral stricture in a series of patients who underwent retrograde intrarenal surgery with using smallest ureteral access sheath. Materials and Methods: Between September 2016 and March 2019, 154 consecutive retrograde intrarenal surgery procedures with adjunctive use of an ureteral access sheath for kidney stone were prospectively included the study. A 9.5/11.5-F ureteral access sheath was used during procedures. The patients were evaluated in terms of intraoperative postoperative and late complications. Ureteral injuries after retrograde intrarenal surgery were assessed visually with flexible and semirigid ureterorenoscope. All patients were evaluated by computed tomographic urography in the first year after treatment for detection of ureteral stricture. Results: The mean age of the patients was 47±15 (12-81) years. Of the patients, 86 were male and 68 were female. Mean stone size was 17.1±8 (7-40) mm and mean operative time was 56±23 (30-120) minutes. Overall 79.9% of patients had evidence of injury to the ureter wall. Non-significant lesion (grade 0) was seen in 39.0% of patients. Grade 1 lesions were assigned in 40.9% of patients. There were no grade 2 and higher lesions detected. A total of 5 patients (3.2%) had minor complications. Urinary sepsis developed as a major complication in 3 patients (1.9%). No ureteral stricture was detected in the patients at first year control. Conclusions: The results of our series indicate that the 9.5/11.5-F ureteral access sheath is safe for routine use to facilitate flexible ureteroscopy and there was no long-term adverse effect.