Introduction <p>Tenosynovial giant cell tumor (TGCT) is a benign tumor that can be treated with arthroscopic synovectomy in largejoints.</p> Case presentation <p>We report the fi rst case of postoperative pseudoaneurysm of the inferior lateral genicular artery, a rare complicationfollowing knee arthroscopy for TGCT. A 31-year-old male presented with pain, swelling, fever, and decreasinghemoglobin level 4 days after arthroscopic subtotal synovectomy for diff use-type TGCT. Magnetic resonance imaging(MRI) and computed tomographic (CT) angiography showed a pseudoaneurysm in the inferior lateral genicularartery. This was successfully treated with coil embolization.</p> Conclusion <p>The case highlights the importance of considering vascular injury as a diff erential diagnosis in patients with severepain and blood loss after arthroscopy, even in tumor-related cases. In addition, it emphasizes the need forappropriate imaging, particularly CT angiography, to accurately diagnose and manage such vascular complications.</p>