Ureteropelvic junction obstruction (UPJO) is a disease often diagnosed in childhood, but it can rarely be detected in adults. Dismembered pyeloplasty is the gold standard treatment method. In this study, we evaluated the success of pyeloplasty in adult patients with UPJO. Material and Methods: We retrospectively reviewed the data of the adult patients who underwent pyeloplasty between January 2012 and July 2021. Preoperative and postoperative differential renal function (DRF), the time required for the clearance of half of the radioisotope from the renal pelvis (T1/2), presence of symptoms, degree of hydronephrosis, anteroposterior (AP) diameter of the renal pelvis, and parenchymal thickness were compared. Results: A total of 30 patients with a mean age of 32.43±7.18 were included in the study. No statistically significant difference was detected between preoperative and postoperative mean DRF (37.6±12.08 and 38±11.35, respectively) (p=0.775). In 19 (63.33%) patients DRF remained unchanged. In 7 (23.33%) patients DRF was improved, and in 4 (13.34%) patients DRF deteriorated. The mean AP diameter and grade of hydronephrosis were significantly improved after pyeloplasty. The ratio of patients with a T1/2>20 minutes significantly decreased from 83.33% to 26.67% (p=0.001). Before the operation 26 (86.67%) patients were symptomatic. After the operation only 8 (26.67%) patients were symptomatic. This change was statistically significant (p=0.001). Conclusion: There were significant improvements in T1/2, AP diameter of the renal pelvis, and the degree of hydronephrosis. Renal function was preserved after the surgery. Also, pyeloplasty was effective in pain relief and should be recommended to adults with UPJO.