Purpose: To investigate the factors that predict the success and complication rates of semi-rigid ureteroscopy (URS) in pediatric population. Materials and Methods: This is a retrospective analysis of the database including 182 patients who underwent URS between 2001 and 2016. The possible factors that might affect the outcome were age, gender, stone laterality, largest stone size, number of stones, stone location, orifice dilatation status, and caliber of ureteroscope. Results: The mean age was 68.1 (7-204) months, and male-to-female ratio was 94:88. Operative side was left for 97, right for 82, and bilateral for 3 patients. One hundred and forty-four patients had a single stone, and 38 patients had multiple stones. The median largest stone size was 7 (2-20) mm. Postoperative ureteral stenting was performed in 150 (86.2%) patients. The overall success rate was 84.6%, while 81.6% and 85.4% in 8F URS and 4.5F URS groups, respectively (p=0.560). Stone-free rate was higher among patients who were older than 36 months, distal ureteral stones and single stones (p=0.012, 0.002, and 0.009, respectively). Complication rate was higher for proximally located stones (p=0.029). The mean follow-up was 23.932.5 months. Conclusion: URS is a safe procedure with acceptable success rates in the pediatric population. Younger age, multiple stones, and proximal location are the predisposing factors for failure, whereas proximal location was the only factor for complication occurrence. Therefore, semi-rigid ureteroscopy should not be the first choice in the treatment of proximal ureteral stones, and alternative methods should be preferred, if available.