In this case, we present a condition where the extension of the hamate hook in the Guyon canal can damage the ulnar artery or its branches, leading to the development of an aneurysm or pseudoaneurysm. The patient, a 12-year-old female, presented to our clinic with a complaint of an uncontrolled palm lump that has been growing for several months and began to bleed in a pulsatile manner after trauma.She was an amateur volleyball player who trained twice weekly for two hours.Color Doppler ultrasound examination revealed a 1.1×0.8 cm pseudoaneurysm in a branch of the ulnar artery. Aneurysmectomy and primary repair were performed.Timely diagnosis and treatment planning are crucial for ulnar artery pseudoaneurysms or aneurysms to prevent ischemic events in a later period.