Background: A rare percutaneous nephrolithotomy (PCNL) complication and its management is reported. Case Presentation: A male patient, 43 years of age, underwent PCNL for a large left pyelocaliceal stone. Surgery was performed in the Valdivia-Galdakao supine position. The percutaneous tract was established by combined radiologic and sonographic guidance. The tract was dilated by balloon and a 24F Amplatz sheath was located. As complete clearance was not achieved because of a residual lower pole caliceal stone, a ureteral Double-J and a 20F nephrostomy were located for a second-look PCNL through the same tract after 7 days. After second-look PCNL residual stone was still not cleared because it was unreachable through the tract established and the patient was discharged without nephrostomy and with the ureteral stent, retrograde intrarenal surgery (RIRS) was planned in 3 to 4 weeks. Hemoglobin, hematocrit, and the renal function were normal. On the seventh day after PCNL, no leakage was detected from the percutaneous tract, but the patient started to complain about flank discomfort and fever. Imaging showed a 6 cm lower pole subcapsular collection. After 3 days of conservative management with antibiotics, the subcapsular collection did not resolve and a percutaneous 6F mono-J drainage in the collection was placed. Drain output was at first purulent and evolved into urine throughout the following days. Drain urine culture was positive for Escherichia coli infection and carbapenemic-targeted antibiotic was offered to the patient. Collection drained about 400 cc in 7 days and the drain was removed when the output was less than 10 cc per day. No late complications were reported and RIRS was scheduled in 1 month to clear the residual stone. Conclusion: Subcapsular urinoma post-PCNL is an uncommon but severe complication. Prompt and correct drainage may solve it.