Aim of the study: Seromas are rarely reported as complications of autologous arteriovenous fistula creation. Case description: An 89-year-old woman was hospitalized for hemodialysis and underwent an autologous arteriovenous fistula creation in the forearm. During cephalic vein expansion using a heparinized saline solution, leakage occurred. A suture was placed to control the leakage, and a Penrose drain was inserted. Serosanguineous drainage ceased on postoperative day two; however, a seroma occurred approximately two weeks after the surgery. Follow-up ultrasonography revealed no growth tendency; therefore, excision and aspiration were unnecessary. Conclusion: This seroma was associated with postoperative dead space, surgical technique, and patient clinical status. Sufficient preoperative ultrasonographic vascular mapping is required to avoid inappropriate handling of veins and prevent seroma formation. Postoperative ultrasonographic follow-up is recommended due to the future risk of fistula dysfunction and infection associated with seroma enlargement, which may necessitate surgical seroma excision.