Background: Carbon-ion radiotherapy (C-ion RT) has the potential advantages in terms of improved dose localization and enhanced biological effectiveness compared to conventional radiotherapy or proton therapy. C-ion RT is expected to contribute to the prolongation of survival in patients with pancreatic ductal adenocarcinoma (PDAC). We started C-ion RT for pancreatic cancer at SAGA HIMAT since April 2014. The aim of this study is to evaluate the clinical results of C-ion RT for locally advanced PDAC. Methods: From April 2014 to May 2016, 76 patients with pancreatic cancer were treated with definitive C-ion RT. 44 patients who were confirmed as unresectable locally advanced PDAC were included in this retrospective analysis. 32 patients were excluded because of resectable disease (n = 8), borderline disease (n = 6), without pathological confirmation (n = 20). C-ion RT was performed with 55.2 Gy (RBE) at 12 fractions in 3 weeks. The anti-tumor effect was evaluating using CT and FDG-PET according to RECIST ver. 4.0. Results: The median follow-up period was 12.8 (range 3.4-27.5) months from the initiation of C-ion RT. In all patients, planned C-ion RT was completed. Induction chemotherapy was performed in 35 (80%) and the median duration time was 3 (range 1-19) months. Forty patients (91%) underwent concurrent chemotherapy with gemcitabine or S-1. Local effect using CT criteria was CR in 2, PR in 5, and SD in 37. The evaluation adding FDG-PET criteria was CR in 25, PR in 6, and SD in 13. Five patients (11%) experienced local recurrence during follow-up period. Two patients who had SD by CT and CR by FDG-PET performed tumor resection and were revealed pathological CR. One and two-year survival rate from C-ion RT were 82% and 66%, respectively. The two-year survival rate from initial treatment was 75%. Only three patients (7%) experienced grade 3 toxicities that were leukopenia, anorexia, and gastric ulcer. There was no grade 4 or 5 toxicity. Conclusions: C-ion RT for locally advanced PDAC was effective and well tolerated. FDG-PET was useful for the evaluation of local effect after C-ion RT.