Background: Pancreatic ductal adenocarcinoma (PDAC) has poor outcome and surgical resection remains the only curative treatment. Post-operative (Post-Op) chemotherapy (CT) improves survival and FOLFIRINOX (FFX) regimen is the standard of care. Increasing number of patients with borderline resectable (BL) or locally advanced (LA) disease are treated with pre-operative (Pre-Op) CT with FFX. However, the benefit of Post-Op CT after Pre-Op FFX remains unclear. The aim of this study was to analyze the impact on survival of Post-Op CT in patients with resected BL or LA PDAC after Pre-Op FFX CT. Methods: 116 consecutive patients treated at the Institut Paoli-Calmettes comprehensive cancer center between 2014 and 2020 were retrospectively analyzed. All patients underwent pancreatectomy after Pre-Op FFX for a BL or LA PDAC. Patients who progressed or died within 3 months after surgery were excluded from the analysis. We compared median relapse-free survival (mRFS) and median overall survival (mOS) defined by time from surgery to relapse or death in patients who received or not Post-Op CT. Results: 116 patients (80% BL, 20% LA) were included: 82 received Post-Op CT (CT+) and 34 did not (CT-). The median number of Pre-Op FFX cycles was 4 in the CT+ group vs 6 in the CT- group. 24 (29.3%) patients received Post-Op FFX, 37 (45.1%) received Gemcitabine, 9 (11%) received Gemcitabine + Capecitabine, and 9 (11%) received a 5FU-based CT. Median time between surgery and first Post-Op CT cycle was 63 days. No difference in mRFS nor in mOS were found between CT+ and CT- groups: mRFS 15.0 vs 13.6 months, HR 1.1 [IC95% 0.69–1.77] and mOS 33.8 vs 36.1 months, HR 0.94 [IC95% 0.55–1.60]. Among patients with pathologic node positive disease (N+) (n = 79), mRFS was 13.9 months in the CT+ group vs 6.9 months in the CT- group (HR 0.68 [IC 0.35 – 1.19]), and mOS was 31.8 months in the CT+ group vs 16.5 months in the CT- group (HR 0.96 [IC95% 0.51-1.81]). Patients who received peri-operative (Peri-Op) FFX (n = 24) experienced longer mOS compared to patients who received Gemcitabine Post-Op CT: NR vs 33.8 months, HR 0.45 [IC95% 0.25-1.02]. Patients who received Peri-Op CT for a total of six months or more (n = 31) had increased mOS (55 vs 32 months, HR 0.61 [IC 95% 0.37- 1.11] and mRFS (16 vs 14 months HR 0.80, [IC95% 0.50 -1.31]) than patients receiving less than 6 months Peri-Op CT (n = 85) Conclusions: Post-Op CT does not clearly impact survival in BL or LA pancreatic cancer pretreated with Pre-Op FFX. We observed a trend in the N+ population for a survival benefit. Peri-Op FFX was associated with longer survival than Gemcitabine Post-Op regimen. Further randomized data are needed to assess the impact of Peri-Op FFX for these patients