Background <p>Perioperative fluorouracil, leucovorin, oxaliplatin, and docetaxel (FLOT) is the standard of care for locally advanced oesophagogastric adenocarcinoma (LA-OGA) in Western countries. However, completing treatment is challenging for patients, particularly in the postoperative setting. This study investigated the impact of adjuvant chemotherapy (ACT) administration and treatment completion on survival outcomes in patients receiving FLOT.</p> Methods <p>Charts of LA-OGA patients treated from 2017 to 2023 were retrospectively reviewed. Survival was analysed using Kaplan–Meier and restricted mean survival time (RMST) analyses, with propensity score matching (PSM) adjustments. Subgroup analyses were stratified by pathological nodal status and tumour regression grade (Mandard TRG). The primary endpoint was 3-year overall survival (OS).</p> Results <p>The study included 233 patients, among whom 62.4% completed the full perioperative FLOT regimen and 21% did not receive ACT. After PSM adjustment, 3-year OS for patients who completed and those who did not complete perioperative therapy was 69% and 57%, respectively (<i>p</i> = 0.09). The 3-year OS was 81% and 52% for patients who did and did not receive ACT, respectively (<i>p</i> = 0.01). In multivariate analysis, completion of perioperative FLOT was independently associated with improved OS (<i>p</i> = 0.04). Survival improvement with ACT was observed in the ypN-positive subgroup but not in the ypN-negative subgroup.</p> Conclusions <p>Perioperative FLOT administration is recommended as the standard of care for LA-OGA. The survival impact of ACT might be influenced by pathological lymph node metastasis.</p>