Aim To evaluate the prognostic value of tumor markers in a European cohort of patients with resectable gastric cancer. Methods We performed a post hoc analysis of the CRITICS trial, in which 788 patients received perioperative therapy. Association between survival and pretreatment CEA, CA 19-9, alkaline phosphatase, neutrophils, hemoglobin and lactate dehydrogenase were explored in uni- and multivariable Cox regression analyses. Likelihoods to receive potentially curative surgery were investigated for patients without elevated tumor markers versus one of the tumor markers elevated versus both tumor markers elevated. The association between tumor markers and the presence of circulating tumor DNA (ctDNA) was explored in 50 patients with available ctDNA data. Results In multivariable analysis, in which we corrected for allocated treatment and other baseline characteristics, elevated pretreatment CEA (HR 1.43; 95% CI 1.11–1.85, p  < 0.001) and CA 19-9 (HR 1.79; 95% CI 1.42–2.25, p  < 0.001) were associated with worse OS. Likelihoods to receive potentially curative surgery were 86%, 77% and 60% for patients without elevated tumor marker versus either elevated CEA or CA 19-9 versus both elevated, respectively ( p  < 0.001). Although both preoperative presence of ctDNA and tumor markers were prognostic for survival, no association was found between these two parameters. Conclusion CEA and CA 19-9 were independent prognostic factors for survival in a large cohort of European patients with resectable gastric cancer. No relationship was found between tumor markers and ctDNA. These factors could potentially guide treatment choices and should be included in future trials to determine their definitive position. Trial registration ClinicalTrial.gov identifier: NCT00407186. EudraCT number: 2006-00413032.