Background Venous coupling devices are widely used during reconstructive surgery involving microvascular anastomosis but have not served as foreign bodies in head and neck surgical site infections. Methods We conducted a case report. Results A patient underwent resection and free flap reconstruction for recurrent tongue squamous cell carcinoma. She developed a neck abscess due to Streptococcus intermedius 7 weeks postoperatively, days after starting chemoradiotherapy. The surgical site infection healed with drainage and antibiotics. Two surgical site infection relapses due to S. intermedius occurred 3 and 8 weeks after completing radiation, the second relapse after a prolonged course of i.v. antibiotics. Surgical exploration revealed a venous coupler within granulation tissue. The device was removed and no further surgical site infection relapses occurred. Conclusion To the best of our knowledge, this is the first report of a delayed‐onset head and neck surgical site infection in which a venous coupler served as a foreign body. An infected foreign body should be suspected in relapsing surgical site infections due to a single organism.