Background To investigate the role of adjuvant radiotherapy in patients with pancreatic cancer. Methods and patients The patients with pancreatic cancer from 18 registered institutions in the Surveillance Epidemiology and End Results (SEER) database were retrospectively analyzed. The characteristics of patients who would benefit from adjuvant radiotherapy were screened, as well as whether neoadjuvant or adjuvant radiotherapy conferred to a better clinical outcome. Propensity score matching was used to control for confounding features. Results Thirty thousand two hundred and forty-nine patients were included in this study (21,295 vs 8954 in surgery and adjuvant radiotherapy group); 1150 patients were matched in two groups. The median survivals in the surgery (S) group and adjuvant radiotherapy (S + R) group were 24 and 21 months, respectively. The 1-, 3-, and 5-year overall survival (OS) rates in the S group and S + R group were 68%, 40%, 31%, and 75%, 30%, 20%, respectively ( p  < 0.001), and the median OS was 22 and 25 months in S and S + R group after PSM, the former 1-, 2-, 3-, and 5-year OS were 73%, 45%, 30%, and 19%, and the later were 81%, 52%, 37%, and 24% ( p  = 0.0015), respectively; stratified analysis showed patients whose carcinoma located at pancreatic head with II stage infiltrating duct carcinoma (22 vs 25, p  = 0.0276), T4 adenocarcinoma (28 vs 33, p  = 0.0022), N1 stage adenocarcinoma (20 vs 23, p  = 0.0203), and patients with infiltrating duct carcinoma received regional resection (23 vs 25, p  = 0.028) and number of resected lymph node were ≥ 4 (22 vs 25, p  = 0.009) had better OS after additional radiotherapy than surgery alone. Patients with pancreatic body/tail carcinoma III stage adenocarcinoma (13 vs, p  = 0.0503) and T4 adenocarcinoma (14 vs, p  = 0.0869) had survival advantage within 24 months for additional radiotherapy. However, patients with T2 stage adenocarcinoma located in pancreatic body/tail had better OS in surgery group than that in R + S group. Conclusions Additional radiotherapy may contribute to improved prognosis for patients with pancreatic head II stage infiltrating duct carcinoma, III stage adenocarcinoma, T4 stage carcinoma, N1 stage adenocarcinoma, regional resection, or number of lymphadenectomy ≥ 4 in infiltrating duct carcinoma. A specific subgroup of patients with specific stage and histological type pancreatic cancer should be considered for additional radiotherapy.