Objectives: To elucidate the prognostic impact of preoperative control of nutritional status (CONUT) scores on gastric cancer patients undergoing adjuvant chemotherapy after radical gastrectomy. Methods: A retrospective analysis of 536 stage Ⅱ-Ⅲ gastric cancer patients undergoing adjuvant chemotherapy after radical resection from Jul 1998 to Dec 2014 was performed. Patients were divided into high (≥3) and low (≤2) CONUT groups with a CONUT score of 3 divided into critical values. Results: The 5-year survival rate of the high CONUT group was significantly lower than that of the low CONUT group (37.3 % vs. 55.7%, P<0.001). Univariate analysis showed that the high CONUT group was associated with larger tumors, more lymph node metastasis, lower body mass index, higher prognostic nutritional index, and preoperative anemia (all P<0.05). Multivariate analysis showed that the CONUT score was an independent prognostic factor for patients with gastric cancer (HR: 1.564, 95% CI: 1.090-2.321, P=0.016). The 5-year survival rate of the high CONUT group was significantly lower than that of the low CONUT group (P<0.05). Conclusion The CONUT score is an indicator for predicting the prognosis of patients with stage Ⅱ-Ⅲ gastric cancer after adjuvant chemotherapy. The nutritional evaluation is helpful to develop a plan for preoperative nutritional intervention.