Purpose We aimed to explore whether the prognosis of patients treated with capecitabine and oxaliplatin (XELOX) or S-1 and oxaliplatin (SOX) regimens who received fewer cycles of chemotherapy after D2 radical resection for gastric cancer (GC) would be non-inferior to that of patients who received the standard number of cycles of chemotherapy. Materials and Methods Data on patients who received XELOX or SOX chemotherapy after undergoing D2 radical resection at Harbin Medical University Cancer Hospital between January 2011 and May 2016 were collected. Results In patients who received 4, 6, and 8 cycles of chemotherapy, the 5-year overall survival (OS) rates were 59.4%, 64.8%, and 62.7%, respectively. Compared to patients who received 4 cycles of chemotherapy, those who received 6 cycles (hazard ratio [HR], 0.882; 95% confidence interval [CI], 0.599–1.299; P=0.52) or 8 cycles (HR, 0.882; 95% CI, 0.533–1.458; P=0.62) of chemotherapy did not exhibit significantly prolonged OS. The 3-year disease-free survival (DFS) rate of patients who received 4, 6, and 8 cycles of chemotherapy was 62.1%, 67.2%, and 60.8%, respectively. Compared to patients who received 4 cycles of chemotherapy, those who received 6 cycles (HR, 0.835; 95% CI, 0.572–1.221; P=0.35) or 8 cycles (HR, 0.972; 95% CI, 0.606–1.558; P=0.91) of chemotherapy did not show significantly prolonged DFS. However, the 3-year DFS and 5-year OS rates of patients who received 6 cycles of chemotherapy appeared to be superior to those of patients who received 4 and 8 cycles of chemotherapy. Conclusions For patients with stage III GC, 4 to 6 cycles of XELOX or SOX chemotherapy may be a favorable option. This study provides a rationale for further randomized clinical trials.