Purpose: The objectives of the present study were to evaluate the feasibility, safety, and efficacy of endoscopic ultrasound (EUS)-guided iodine-125 (125I) seed implantation in ampullary carcinoma (AC). Material and methods: From January 2011 to June 2020, 13 patients were selected for this retrospective study. Thirteen tumors (27.46 ±12.07 mm) were treated with EUS-guided 125I seed implantation in 29 sessions. We evaluated the therapeutic efficacy, adverse effects, and overall survival (OS) time. Results: Complete response (CR) was observed in one tumor in 6 months. Partial response (PR) was detected in two target tumors in 3 months, seven in 6 months, seven in 9 months, and six in 12 months. Good periods of survival were observed. The median OS was 35 months, 95% confidence interval (95% CI) was 8.97 to 61.03 months. The 1-, 2-, and 5-year OS rates were 100%, 67.5%, and 11.3%, respectively. There were no procedure-related deaths or serious adverse events. Transient abdominal pain (5 cases, 17.2%), abdominal distension and loss of appetite (3 cases, 10.3%), and seed migration (1 case, 3.4%) were observed, respectively. Conclusions: In selected patients with inoperable AC, EUS-guided 125I seed implantation is feasible and safe with favorable local control efficacy and OS. [ABSTRACT FROM AUTHOR]