Congenital obstructive uropathy is a rare cause of ascites in infants. Majority of reported cases of genitourinary causes of ascites were due to posterior urethral valve. Here, we report a 6-month-old boy who presented with progressive tense ascites and peritonitis attributed by unilateral left distal ureteric obstruction and acute pyonephrosis. He underwent left nephrostomy placement, after which there was a remarkable improvement of ascites. He then underwent left ureteral diversion procedure a month later with a tentative plan for ureteral reanastomosis in 6 months. To date, there are no reports describing ascites secondary to distal ureteric obstruction beyond the neonatal period. The objective of this case report is to highlight unilateral urinary tract obstruction as a potential cause of transudative ascites. Additionally, the superimposed infection in the obstructed collecting system can lead to acute peritonitis likely due to translocation of bacteria into the peritoneal cavity.