BACKGROUND Percutaneous nephrolithotomy (PCNL) is indicated for large renal calculi (≥2 cm) and is often the treatment of choice due to its high success rate. Guidewire fragmentation is a rare procedural accident that can occur in PCNL but may be missed. Retention of the fragment within the upper urinary tract can lead to further complications, such as recurrent nephrolithiasis or impairment of renal function. CASE REPORT We present the case of a 54-year-old man who experienced right flank pain for 5 days. His history was significant for recurrent nephrolithiasis, managed by PCNL in other hospitals. The most recent procedure was conducted 4 years ago, and his perioperative course was uneventful. Preoperative computed tomography revealed right renal calculi and a C-shaped foreign body. He was scheduled for an elective PCNL. The foreign body was intraoperatively identified as a guidewire fragment and removed. CONCLUSIONS Currently, there is no standard management for intrarenal foreign bodies. Suspicion should be raised in young patients with recurrent stones within a short period of time. A thorough history on past urological interventions should be obtained. Symptoms can also have an insidious onset that could mimic nephrolithiasis or urinary tract infections. Extraction can be done via a standard minimally invasive approach. It is also the surgeon's responsibility to check the integrity of intraoperative instruments so as to minimize risks of complication and reassure the patient.