BackgroundPost-traumatic, true aneurysm of the hand is a well-documented phenomenon. Hypothenar hammer syndrome is often a consequence of repeated blunt trauma to the palm, but a false aneurysm, or pseudoaneurysm, of the palm is much rarer. A pseudoaneurysm is often the result of focal penetrating trauma. ObjectivesThe goal of this article is to describe a rare case of a child with a pseudoaneurysm of the superficial palmar arch and his subsequent surgical treatment. Case ReportA 3-year-old boy sustained an accidental laceration to his palm while picking up a knife from a counter. The child was initially treated in a local Emergency Department (ED) with local wound care and Dermabond (Ethicon, Inc., Somerville, NJ). No imaging was undertaken at that time. The boy subsequently developed a large, pulsatile, painful mass in his palm near the site of injury, and he presented to our ED for evaluation. Using a combination of imaging modalities and a careful history, the boy was accurately diagnosed with a pseudoaneurysm of the superficial palmar arch. This lesion was subsequently successfully resected and repaired. The child has healed well after surgery, with no lasting sensory or motor deficits to the hand. To date, this is one of only two reported post-traumatic pseudoaneurysms of the palmar arch in a child in North America. ConclusionAlthough a rare phenomenon, pseudoaneurysm of the superficial palmar arch after local penetrating trauma remains an important item on the differential for patients presenting with palmar masses. Pseudoaneurysm can be effectively diagnosed and treated with excellent results.