Urologic congenital anomalies associated with ureteropelvic obstruction (UPJO) have been previously characterized; however, less data are available regarding these associations in a prenatally diagnosed population. A retrospective study was conducted to evaluate significant clinical features and urological anomalies associated with prenatally diagnosed UPJO. The records of 143 children with prenatally diagnosed hydronephrosis secondary to UPJO were retrospectively reviewed. The gender, side of obstruction, degree of hydronephrosis, associated clinical features, and urological anomalies were noted. Hundred and forty-three children (M/F = 2.7) with a total of 198 affected renal units (RU) presenting with unilateral (61%) or bilateral (39%) UPJO were enrolled. In cases of unilateral obstruction, the left side was affected in 60 children (68%). The grade of hydronephrosis was Grade 1 in 56 RU (28%), Grade 2 in 51 RU (26%), Grade 3 in 50 RU (25%) and Grade 4 in 41 RU (21%). Associated clinical features included prematurity (n = 7, 4.9%), twinning (n = 5, 3.5%) and presentation with renal failure (RF) (n = 2). Excluding contralateral UPJO, other urologic anomalies were encountered in 29 patients (20.3%). Associated vesicoureteral reflux (VUR) was encountered in 11 patients (7.7%, M/F = 2.7). Pyeloplasty was required more often in children with associated VUR (54.5 vs. 18.2%) (P = 0.01). Contralateral multicystic dysplastic kidney (MCDK) was encountered in six patients (M/F = 2), one of whom presented with RF. One child carried the diagnosis of Schinzel-Giedion syndrome (SGS), demonstrating severe developmental and neurological disorders and bilateral hydronephrosis. The more frequent occurrence of UPJO in males with predominantly left-sided location, association with VUR and MCDK, and increased frequency of bilaterality in our prenatally diagnosed patients were similar to historical reports. In addition, prematurity and twinning were independently associated with UPJO. The higher rate of pyeloplasty in patients with associated reflux warrants further investigation.