Aim: In this study, we aimed to demonstrate the effect of mirabegron on ureteral access sheath (UAS) placement during flexible ureterorenoscopy (f-URS). Material and Methods: The study enrolled 96 patients with renal stones who underwent fURS between October 2019 and March 2020. The patients were divided into 2 groups. Mirabegron treatment was administered 2 weeks before fURS in Group 1 (n = 41), and no mirabegron treatment was given in Group 2 (n = 55). All operations were performed by a single surgeon (MK). Demographic characteristics were recorded for each patient, including age, body weight, height, body mass index (BMI), stone characteristics, and perioperative data, including operation-fluoroscopy durations, stone-free rates, complications, and surgery success rates. Group data were compared, and p-values less than 0.05 were considered statistically significant. Results: No significant difference was detected between the groups in terms of age, sex, body mass index, number and size of stones, side of stones, density of stones, and renal hydronephrosis level. UAS placement in Group 1 was found to be statistically significant at the first attempt (without using a semi-rigid ureteroscope or balloon dilatation) compared with Group 2 (p=0.001) Discussion: The use of mirabegron may facilitate UAS placement during fURS with less operation time and fewer complications.